ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 389 



arranged. The nuclei at first are evenly distributed through the cyto- 

 plasm, but with the appearance of the vacuoles they move away to a 

 distance equal to about three or four times their diameter and lie at the 

 surface of the denser layer of cytoplasm. Gradually the vacuoles in- 

 crease in length with a narrowing of their transverse diameters. The 

 capillitial thread is at first nodular and uneven, but as it gains its per- 

 manent form — a contorted tubular opening through the cytoplasm — its 

 membrane becomes more distinctly differentiated as the. wall of the 

 future capillitial thread. A striking feature of the whole process is the 

 formation of fibrillar asters which appear about the capillitial vacuoles. 

 They consist of delicate fibrillar strands extending from the developing 

 cupillitium in all directions through the surrounding cytoplasm. They 

 are oriented on deeply staining granules which are abundant in the 

 region of the vacuole, either on the surface of the thread or at some 

 disoance from it. Possibly their normal position is on the thread. A 

 granule on the surface may be the centre for rays that run in several 

 directions from it, only one of which is radial to the capillitial tube. 



The authors discuss the significance of the various processes : 

 1. They are initiated by the liberation of water and the formation of 

 vacuoles. 2. The vacuolar sap at first contains materials in solution, 

 which are apparently precipitated in fixation, and which later disappear 

 and probably furnish material for the capillitial wall and spirals. 3. The 

 spirals are laid down as organized material, in a definite form on the 

 outside of the thread next to the vascular membrane, although functionally, 

 the position of the spiral on the inside of the thread would be also 

 hygroscopically effective. 



Plasmodiophoracese and their Relationship to the Mycetozoa and 

 Chytrideae.* — E. J. Schwartz has studied the root-parasites of Belli* 

 perennis, Mentha pulegium, and Alisma plantago, and concludes, from a 

 cytological point of view, that the genus Ligniera, in which the organisms 

 have been placed, belongs to Plasmodiophoracea?. He compares the dif- 

 ferent families, and finds that the cruciform type of nuclear division 

 and the presence of the akaryote stage are constant in the Plasmodio- 

 phoracese and in Olpidhim, but are lacking in Mycetozoa. In the three 

 families there are two types of nuclei, vegetative and reproductive, and 

 an absence of Karyogamy prior to spore-formation. 



In the Mycetozoa nuclear divisions are karyokinetic. The Plasrno- 

 diophoracege, though closely related to both the Mycetozoa and Chy- 

 tridea?, are best considered as a separate class. The spore mother-cells 

 in the zoosporangium of Olpidium each give rise to four zoospores, and 

 in the Chytrideae the zoospores conjugate in pairs. The myxamoebaj in 

 the Mycetozoa also conjugate, and there is nuclear fusion as well. 



* Ann. of Bot.,xxviii. (1914) pp. 227-40 (1 pi.). 



