This paper deals with a florula found in the Pailuyuan Sandstone Formation of the district Weinan of central Shensi. The age of this bed is assigned to Late Eocene. From this bed, a large amount of the leaves of Palibinia pinnatifida (Reid et Chandler) comb. nov., P. korowinii Vassilevskaja and P. latifolia Kor. has been collected. Other leaves found in this bed belong to the genera Ulmus, Corylus, Sophora, Rosa, Spiraea, Crataegus, Campylotropis, Lespedeza and Salix (?) and the family Apocynoaceae. Palibinia pinnatifida was first described by Reid and Chandler in 1926 in the Bern- bridge Flora of England, as Dicotylophyllum pinnatifidum; but in 1932, Korowin further described some other specimens under the name Palibinia densifolia from the Ar-Oeln bed of Turkemania, Central Asia. Judging from the form and venation of these leaves, they are definitely of the same species. According to the International Rules of Botanical Nomenclature Palibinia should be adapted for this kind of plant, as the generic name Dicotylophyllum is too vague to be used for this peculiar linear pinnatifid leaves. Palibinia is rather difficult to be distinguished from Myrica, Comptonia, Banksia and Dryandra, yet it can be recognized under the critical examination of the venation. However, it is a form genus of doubtful affinity and is supposed to be a group of extinct woody plants, with coriaceous, alternate, linear pinnatifid leaves. The segments are round, with pointed apex. The primary veins appear quite strong. Each segment possesses a secondary vein, arising at an angle of 45–65º running stright forward, up to the apex, with a branch vein directed towards the sinus immediately below. Sometimes one or two interstitial veins are present between the secondary veins. Of which, the pinnatifid leaves of coriaceous nature, the tertiary veins directed towards the sinus below, and one or two interstitial veins developed between the lateral reins are the chief distinctive characters. Palibinia was found only in the Upper Eocene beds in England and Central Asia. It was usually associated with some tropical or subtropical plants, such as Cinnamomum, Sabal, Banksia, Grevillea and Myrica. In the present bed, plenty of Ephedra pollen grains have been secured. All the leaves described here are quite small and coriaceous. These indicate that the climate of central Shensi during the Late Eocene was rather warm and dry.

Three-day old and seven-day old rice seedlings (Oryza sativa L. variety Yinfang) were treated under oxygen-deficient condition (by substituting the air with nitrogen in sealed glass bottles). Localization of cytochrome oxidase and polyphenol oxidase in roots were determined histochemically at fixed intervals after treatment (8, 24, 32, 48, 72 and 96 hours). The results obtained in this investigation may be briefly summarized as follows: 1. Polyphenol oxidase and cytochrome oxidase are detected in the seedlings from the second day of germination. 2. Maximum activity of polyphenol oxidase in the root tip appears on the fourth day of germination but it decreases progressively thereafter. In the vascular bundles of maturation zone, however, the enzyme activity is found to increase continuously with in- crease in age. If oxygen supply is limited or is withdrawn, a sharp decrease of enzyme activity occurs after 8 hours of treatment. It continues to decrease rapidly and almost disappears after about 48 hours. 3. The activity of cytochrome oxidase increases steadily up to the 10th day of germination when it reaches its plateau and is maintained at such a level thereafter. Under the condition of limited oxygen supply, the enzyme activity decreases but it still shows relative increases in activity as the plant grows. It appears likely that adaptive formation of this enzyme occurs during oxygen deficiency. On the basis of the observed results, one may suggest that the adaptation of cytochrome oxidase to limited oxygen supply probably plays an important role in the tolerance of rice to submergence under water. 4. The results show that these two types of terminal oxidases are more sensitive to oxygen on the third day than on the seventh day of germination.

There are two opposite opinions as regards the mechanism and the path of downward oxygen transport in rice and other higher plants. Van Raalte (1940), Yamada (1952), and others maintain that an oxygen pressure gradient of decreasing magnitude from the stem base down to the root tip exists in the intercellular air spaces, which are interconnected throughout the cortex, and the oxygen transported therein is in free molecular form and moves about by diffusion along its own gradient. Recent diffusion experiments in plants by Barber (1962), employing radioactive O15 as indicator, gave direct confirmation of this hypothesis. The opposite view is held by Brown (1947), Soldatenkov (1963) and others. They consider that the passive diffusion of oxygen along its own gradient is inadequate to account for the actual amount transported downwards. The fact that downward oxygen transport in roots comes almost to a standstill, once the aerial part is removed while the cut end of the short stump is still left in air, casts doubts as to the validity of the diffusion hypothesis; and is in favour of their claim that in addition to, or in placement of, diffusion, active participation of living tissues in shoot is necessary to drive enough oxygen to meet the demand of roots. The oxygen in active transport is no longer in free gaseous state but is in dissolved or combined form (as in peroxides) and moves presumably along the vascular bundles in a way which is hitherto unrevealed but is apparently dependent upon the physiological activity of the conducting tissue. In our previous report (Lou et al 1964), we gave data based on quantitative measurement of the amount of oxygen transported downwards from aerial to submerged parts in intact seedlings with the respiratory hydrometer specially designed for the purpose. In seedlings of marshy plants (e.g. rice), it amounts to about 50% of the total oxygen absorbed by the aerial part; in water cultured seedlings of ordinary land plants (e.g. pea), 20%–30%. By deliberately blocking the alternative paths of oxygen transport in seedlings, one at a time, and measuring the downward oxygen transport accordingly in the same way as before, we should be able to decide which one of the two paths is mainly responsible for the transport. The blocking can be conveniently carried out at the upper end of the radical in a pea (or broadbean) seedling by surgical treatment (see Fig.1); either by ringing off the peripheral cortex where most of the air spaces reside; or by piercing through the central cylinder, within which the vascular bundles are confined. The treated radical is then submerged in water and ready for measurement. Without recourse to surgical treatment and mechanical injury, the air space in the cortex can also be blocked by displacing its air content with water through vacuum infiltration. The present investigation has shown that when the intercellular spaces in the cortex of the radical are blocked either by ringing or by infiltration, the aerial part of the treated seedling absorbs much less oxygen than the control as though its radical were completely severed (Table 2); or, in other words, the downward oxygen transport is effectively stopped by such a means. On the other hand, interruption of vascular bundles in the central cylinder only reduces the amount of oxygen in transport to less than one half, which can be accounted for by the combined effect of the reduced root activity due to shortage of food supply and the unavoidable partial disruption of the peripheral cortex. Besides taking actual measurement, downward oxygen transport in intact pea (or broadbean) seedlings can also be detected by simply noticing the growth rate of its radical. As is shown in this investigation, the radical ceases growing in still water, if the oxygen supply from its aerial part is interrupted. As a result of oxygen deficiency, the radical tip deteriorates in a few days. These effects can be easily realized by ringing off the cortex or by infiltrating its air spaces with water. That the peripheral ringing of the radical does no harm to its growth process is revealed by the fact that if air is bubbled through the water culture steadily, normal growth ensues. The above results leave no doubt that in seedlings of rice, pea, and broadbean, downward oxygen transport mainly takes place in the intercellular spaces in the radical cortex, and seems to have no concern with the activities of vascular bundle and cortex. Although there are evidence that rice roots may actively secrete oxygen in the form of peroxides to its immediate neighborhood (the rhizosphere), the actual amount and the distance traversed in such an active transport however, is very much limited and is insignificant as compared with that taking place in the intercellular spaces.

The structure, growth and mitotic activity of 211 shoot apices of developing sprouts of Syringa oblata var. affinis Lingelsh. in longitudinal sections and 67 in transverse sections have been studied with the view to understanding the nature of zonation patterns and cytogenesis of the apical meristems during a double plastochron. The external morphology and the anatomical structure of the apices in 4 plastochronic stage-early, middle, late Ⅰ and late Ⅱ stages are described. In the shoot apices examined, especially those at late plastochronic stage, the following zones may be delimited: Zone of tunica initials, zone of corpus initials, peripheral zone and zone of rib meristem. The location and orientation of mitotic figures observed in longisections of the apices in 4 plastochronic stages are plotted in diagrams and the mitotic frequency has been calculated. Information obtained from these investigations reveals that the tunica and corpus inititals constitute an active region of the apex, but their mitotic activity changes periodically within the double plastochron. In the middle plastochronic stage when the apex is at its minimal area and the cells of peripheral zone and rib meristem zone have been completely transformed into constituent parts of foliar primordia and the subjacent tissues of the stem and the pith mother cells respectively, the mitotic frequency of the initials is at its maximium and its intensity of mitotic activity is not much lower than that of any other meristematic zone at any stage. When the apical dome is reformed by the activity of these initials in late plastochronic stages, the mitotic frequency of the initials gradually drops and the region of high mitotic frequency shifts to the flank of the apex, the peripheral zone. Anticlinal divisions are predominant in this zone. On the other hand, those cells directly left behind by the corpus initials, which constitute the rib meristem, are vacuolated and marked by the pre- dominance of transverse divisions. Thus the entire zonation pattern reappears. In the next early plastochronic stage, the mitotic frequency of the tunica and corpus initials drops to its mimimium, but other regions of the apex still maintain a high mitotic frequency. It may be concluded that the tunica and corpus initials form a cytogenerative center of the shoot, and the cytohistological zonation is actually a result of the fact that different regions of apical meristems are different in mitotic activety, different in state of cell differentiation and different in their function in morphogenesis.

The present investigation deals with the effect of coconut milk upon the growth of in vitro culture of young Ginkgo embryos. The basic medium consists of White mineral salts in which Fe-citrate was used instead of Fe2(SO4)3 and vitamins (B1, 0.5 ppm, B6, 0.5 ppm, Ca-pantothenate, 0.5 ppm, niacin, 1 ppm and glycine, 2.5 ppm). 8% sucrose was used for younger embryos as the carbon source and 5% for the larger ones. The pH value of the medium was adjusted to about 6. 0.7% agar was used. The cultures were kept in an incubator (about 20–23 ℃) and no artificial light was used. The coconut milk, both filtered and autoclaved, was tested for its effect on the growth and structure of the young embryos. The important results obtained are summarized as follows: 1. The coconut milk, used both filtered and autoclaved, greatly promoted the growth and differentiation of the Ginkgo embryos cultured in vitro. 2. The optimum concentration of the coconut milk is 10%–20% for the younger embryos (900–1,600μ), while the higher concentrations (30% and over) may induce callus formation. 3. For the larger embryos the coconut milk was less effective, no callus formation occurred for the embryos over 2,800μ at isolation and for them 40% coconut milk was found more effective than 10% coconut milk. 4. There was no significant difference of the effect between the filtered and the autoclaved coconut milk. 5. From the experimental data obtained the authors conclude that the coconut milk at adequate concentration greatly promotes the rate of cell division and may initiate the meristematic regions around the shoot apex and over the whole surface of the cotyledons of the treated embryos.

The branches of successive orders of the inflorescence of Panicum miliaceum L. arise in the axils of the bracts of the branches of next lower order. Their initiation is evidenced by periclinal division of sub-hypodermal cells. The primordia of branches arise in initiation like a normal axillary bud. The floral histogenesis of Panicum miliaceum L. is similar to that of Triticum. Primordia of the spikelet, flower and stamen are initiated by the activity of the periclinal division of the sub-hypodermal cell or cells. Sometimes, periclinal divisions also occur in a few hypodermal cells during these primordial developments; such divisions are more frequent in the formation of the flower and stamen primordia than in the formation of the spikelet primordia. The periclinal division of the dermatogen ceils never occurs in the formation of these organs. Glumes and lemma are initiated in the periclinal division of the dermatogen and hypodermal cell or cells. The primordia of the palea, lodicule and carpel are initiated by means of the periclinal division in the dermatogen cell or cells. In the formation of the palea and carpel, periclinal divisions also occur in hypodermat cells, but their derivatives are protruding into the bases of the primordia and do not constitute the tissues of the palea and carpel. The growing point of the flower axis develops into the ovule. The integuments arise from the periclinal division of dermatogen cells. The periclinal division of dermatogen cells is characteristic of the initiation of the phylloid organs in the Gramineae.

In the literature, the information on the correlation between the material changes and the cold resistance of plants is full of contraditions, especially in regard to the changes of the sugar and protein contents in connection with the development of the cold resistance in hardened condition. The present work was undertaken with an attempt to study the changes of the intracellular materials of wheat in the overwintering period with cytochemical methods. The wheat varieties used in this study were the same as used in our previous work (Chien and Wu, 1965), these are, 2 winter varieties (Nungta 183 and Huapei 187), 2 spring varieties (Nanta 2419 and Piyü), and 2 intermediate ones (Pima No. 1 and Pingyaian 50). The plants of the different varieties were cultivated under the same environmental conditions. Samples were collected and fixed at the same time (twice a month from October to March). For making microscopical preparations, the sections of materials for comparative studies were mounted on the same slide, so that they all were subjected to exactly the same treatment. The results obtained are summarized as follows: 1. The starch content in the cells of the tillering nodes increased, as the temperature fell in autumn. The starch grains gradually disintegrated when the plants came in hardened period (late October to mid-November), and completely disappeared in severe winter (January). They were regenerated in mid-February. 2. The soluble sugar gradually increased with the falling of the temperature in late autumn and steadily increased until the temperature approached 0 ℃. However, when the temperature dropped further, the soluble sugar content decreased and finally in March reached the level which it assumed before winter. 3. It was determined by cytochemical reactions that the cytoplasmic proteins and RNA and the nuclear basic proteins increased from late autumn to early winter. The degree of these changes showed apparent difference between the different varieties. Based on the phenomena observed, the authors discussed their correlation with the cold resistance of wheat plants. 4. The fat and lipids were also tested, but there was no indication of the occurrence of these substances in the winter season. The study on the DNA content revealed no correlation of any kind with the development of the wheat hardiness.