ZOOLOGY AND ROT AX Y, MICKOSCOPY, ETC. 593 



Insolation and temperature were found to exert an influence on the 

 inception of xylem-formation, and experiments seem to show that the 

 colour of the bark may also l)e an important factor. The results of 

 further investigations will be published later. 



Root-structure of Smilax.*— W. A. Tichomirow has made a com- 

 parative study of the root-structure of Smilax excelsa and *S'. aspera. 

 The most striking characteristic of both species is the two-layered 

 endodermis. Two types of this endodermis are frequently found in the 

 same root. In the first type both layers have strongly thickened cell- 

 walls, the inner walls being especially thick ; the cells of the inner layer 

 are almost rectangular and tangential ly elongated when seen in cross- 

 section. In the second type the cell-walls are much thinner, especially 

 those of the inner layer, but the outline of the cells resembles that of 

 the first type. This polymorphism of the endoderm-cells is much more 

 marked in S. aspera than in >S'. excelsa. The cortical-cells of *S'. excelsa 

 are composed of well-defined spongy parenchyma ; the cortex of S. 

 aspera is similar, but less well-defined. The starch-grains of S. excelsa 

 are compound, while those of S. aspera are simple. In other respects 

 the root-structure of both these species is quite normal. 



Keproductive. 



Embryology of the PodostemaceaB.f— AV. Magnus has studied the 

 following species of the Podostemaces — Laivia zeylanica, Podostemon 

 subulatus, Dicrsea elongata, Hydrohrium olivaceum, Farmeria metzgeroides, 

 and finds that, notwithstanding certain striking differences, the embryo- 

 logy has much in common with that of other Angiosperms. The 

 sheathing of the nucellar cavity with a more or less water-tight covering 

 formed from a cuticularized inner integument, finds a parallel in 

 Raphanus and Arahis. while a similar condition is common in many of 

 the families belonging to both the Choripetalie and the Sympetalae. 

 This sheath, known as the embryo- dermis, appears to protect the food- 

 reserve of the embryo in the Angiosperms, and is therefore not peculiar 

 to the Podostemaceas, the only peculiarity being its early development. 

 The thickening of the cells at the base of the chalaza is a common 

 feature in many Angiosperms, and appears to be a device for maintain- 

 ing a connexion between the emljryo-sac and the funicle ; in the 

 Podostemaceas this thickening appears earlier and proceeds more quickly 

 than usual. The breaking-down of the nucellar tissue is only a special 

 case of a wide-spread phenomenon. The formation of the egg-apparatus 

 in Podostemon, Hydrobrium, and Farmeria resembles that of Gypripedium, 

 several Onagraceae and Campanulaceas; but the condition of Dicrsea is 

 unique, since neither the micropylar nor the chalazal parts of the 

 embryo-sac form more than two cells, and the ^g^^ itself results from a 

 division of the micropylar nucleus. The author believes that the eight 



* BuU. Soc. Imp. Nat. Moscow (1912) pp. 401-19 (3 pis.). 

 t Flora.. V. (1913) pp. 275-336 (4 pis. and 41 figs.). 



Dec. 17th, 19 J 3 2 R 



