ZOOLOGY AND BOTANY,*MICROSCOPY, ETC. 735 



growth of the cell ; separation takes place through irregular growth, 

 especially in the longitudinal direction. In the turgescence mechanism 

 separation results from the disarrangement of thin-walled turgescent 

 cells and shrivelled dead cells. Both the anatomical and physiological 

 characters of the different separation mechanisms may vary in the same 

 species under the influence of internal and external factors. The me- 

 chanisms are not sharply separated from one another, but pass by tran- 

 sition into one another. 



Reproductive. 



Megasporophyll of Saxegothasa and Microcachrys.* — R. B. Thom- 

 son has studied " some neglected phases of the inversion of the spor- 

 angia! supply-bundles of "both the staminate and ovulate cones" of 

 Saxegothsea and Microcachrys. The author regards the fertile scale as 

 a simple structure, and as homologous to the microsporophyll in both 

 Saxegothsea and Microcachrys, and probably in the whole of the Taxaceas. 

 With this group is also associated the Araucarieae ; and thus in the two 

 simple scale-groups the microsporangia and Ehe megasporangia are on 

 opposite sides of the sporophyll, and as their ancestral homosporous forms 

 usually have the sporangia on the lower surface, " the ovule has probably 

 1 leen transferred to the upper surface iu the course of phylogeny." 



Closing' of the Micropyle of Gymnosperms.f — W. Himmelbaur has 

 studied the phenomenon of the closing of the micropyle in Gymnosperms, 

 especially in Larix. The author finds that the epidermal and sub- 

 epidermal cells of the free ends of the integument become greatly 

 disorganised and cutinised. The outer wall of the integument becomes 

 much elongated, and bends inwards towards the micropyle, so that the 

 inner cutinised mass, with the pollen-grains adhering to it, is borne 

 into the interior of the seed. It would appear that the sticky material 

 developed in connection with the cutin serves to hold fast the pollen- 

 grains, and that the bending-in of the integument serves as a sort of 

 pollen-tube for bringing the pollen-grains into contact with the nucellus, 

 and also protects the former between pollination and fertilisation. The 

 whole arrangement is a relic of the independence of the sexual genera- 

 tion. 



Structure of the Antennas in Catasetum.J — H. von Guttenberg 

 has made a study of the antennas of eight species of Catasetum, and finds 

 that in G. barbatum, G. cernuum, C.fimbriatum, G. ornitltorhynchos, and 

 C. Trulla, there are no sensitive papillae, but they are present in G. 

 callosum, G. tridentatum, and G. splendens. In those species which have 

 no papilla the antennas themselves act as sensitive threads, which transfer 

 every movement to a basal joint ; and in connection with this function 

 various modifications of the antennas are to be observed, the most usual 

 being a thickening or lignification of the turned-in edges, which may 

 extend to the very tip of the antennas, and at the same time a weaken- 

 ing of the cells at the joint. In G. ornithorhynchos there are sensitive 



* Bot. Gaz., xlvii. (1909) pp. 345-54 (4 pis.). 



t SB. k. Akad. Wiss. Wien, cxvii. (1908) pp. 3-24 (2 pis. and 2 figs.). 



X Tom. cit., pp. 347-68 (2 pis.). 



