ZOOLOGY AND BOTANY, MICROSCOPY, ETC. l7o 



April divide to form the generative and the tube nuclei ; the division of 

 the former probably occurs after the shedding of the pollen. 



The archesporium of the megasporangium is not differentiated till early 

 in March, and consists of a single hypodermal cell ; the adjacent cells show 

 gradations in size and characteristics of potential archesporial cells. The 

 archesporium functions directly as the megaspore-mother-cell and reaches 

 maturity about the middle of April. The reduction-division of the 

 megaspore-mother-cell takes place the last week of April, and two 

 megaspores are found about a week later. 



Embryology of Rhus and Coriaria. — J. Grimm has studied the 

 flowers of Rhus and of Coriaria^ and confirms the opinion expressed 

 by Eobertson that the dioecious condition of R. Toxicodendron is of 

 recent origin, for the male flowers often produce female organs, which 

 develop in exactly the same way as in the female flower, and form a 

 rudimentary but complete embryo-sac with egg-apparatus, central 

 nucleus, and antipodal cells. By the fusion of the three carpels, a mass 

 of conducting tissue is formed, which, however, is only perfected in the 

 fertile carpels of the female flower. The embryo-sac has an open micro- 

 pyle and a hypostase at the chalazal end. The development of the 

 pollen is normal, the haploid number of chromosomes being fifteen and 

 the diploid thirty. The pollen-tube passes along the conducting tissue, 

 traverses the space between the carpel and the ovule, enters the funicle, 

 along which it makes its way as far as the chalaza, finally entering the 

 embryo-sac from the side or near the apex. Fertilization is normal and 

 double. The above description also applies to the embryology of 

 R. typhina and R. glaljra, and of Coriaria myrtifolia and G. terininalia, 

 but in the two former species, parthenocarpy may take place if fertiliza- 

 tion does not occur. 



CRYPTOGAMS. 



Pteridopliyta. 

 (By A. Gepp, M.A. F.L.S.) 



Psaronius brasiliensis.* — F. Pelourde gives an account of the two 

 specimens of Psaronius brasiliensis (a paleozoic member of the Marat- 

 tiales which were collected in Brazil by Guillemin and by Martins. 

 A careful investigation of their structure leads him to say that they 

 are specifically identical. And he calls attention to (1) the great 

 clearness of the parenchymatous areas of stem and root, which rendered 

 these latter coalescent for the greater part of their length ; (2) the 

 constant presence of lacunse in the internal bark of the roots ; (3) the 

 large shape of the gum-cells, and their frequent joinings two or three 

 together ; (4) the form of the ligneous stars and the shallowness of their 

 inter-polar sinuses. The three latter characters combined suffice to dis- 

 tinguish F. brasiliensis from all other known types of the genus. 



* Flora, iv. (Jena, 1912) pp. 309-334 (2 pis. and 3 i^gs.). 

 t Ann. Sci. Nat., ser. 9, xvi. (1912) pp. 337-52 (figs.). 



