ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 449 



The vegetative cells are ccenocytic, and the zoospores are formed by an 

 almost' simultaneous constriction of the strands which connect the 

 various masses of cytoplasm round the individual nuclei. When the 

 oogonium develops there are 35-55 nuclei included in the cell which 

 migrate to the periphery and peripheral vacuoles arise between them. At 

 the same time many small, isolated fine-meshed, patches arise in the 

 central cytoplasm ; these then migrate to the centre of the oogonium, 

 where they fuse into one conspicuous, deeply-staining, fine-meshed mass. 

 The periplasm becomes divided by anticlinal walls into a great number 

 of cells, which are hexagonal in surface view ; the cells are bounded 

 only by a plasma membrane at the outer surface, which is directed 

 towards the oogonium wall. The mature oosphere is uninucleate. The 

 antheridium contains numerous nuclei, but only a single sperm nucleus 

 is introduced into the egg. No antheridial tube was observed, but the 

 egg shows a distinct receptive papilla which develops a tube from the 

 inner margin of the peripheral cells to the oogonial wall. As the sexual 

 nuclei approach they invariably put out a pointed beak upon their 

 adjacent surfaces, and these beaks may come in contact ; actual fusion 

 seems to be delayed until some point not ascertained, after the oospore 

 wall has thickened. Araiospora is placed between Pythium and the 

 Saprolegniaceae. < 



" Bios " of Wildiers.* — It was shown in 1901, by Wildiers, that 

 pure beer-yeast is not able to develop and ferment rapidly in Pasteur's 

 solutions with sugar, unless a sufficient quantity of an extract obtained 

 by boiling the same yeast is added to the solution. The unknown 

 substances contained in this extract were termed by the discoverer 

 "bios." A. Amand has made further investigations of this peculiar 

 action, but without throwing any light on the nature of the active 

 substance. 



Sexual Reproduction in the Rusts. f — ■ A. H. Christman has in- 

 vestigated the early stages of development of the gecidium in Phrag- 

 midium speciosum and Gceoma nitens. The early stages of development 

 were the same as those described by Blackman for Phragmidium viola- 

 ceum, but after the sterile cells have been cut off the " fertile cells " 

 fuse in pairs by the breaking down of the upper part of the wall that 

 lies between them. Only the cytoplasmic masses, however, fuse ; the 

 nuclei remain separate, but divide by the well known method of " con- 

 jugate" division, which takes place in the upper part of the cell ; there 

 the aecidiospores and intercalary cells are formed. Similar fused 

 "fertile cells" were observed in Uromyres Caladii, but the early stages 

 were not traced. 



Structure and Development. 



Vegetative. 



Stipular Formations. J — J. Schiller t^ives the results of his observa- 

 tions on the relation between true stipules and pseudo-stipules ; the 



* La Cellule, xxi. (1904) pp. 329-346. 



t Bot. Gazette, xxxix. (19 >5) pp. '2<J7-7 . pi. 8. 



X SB. K. Akad. Wiss., cxii. (1903; re-eived May 1905) pp 703-819 (3 pis.;. 



Aug. 16th, 1905 2 h 



