UROMYCES ALOES COOKE. 



659 



which lose their contents. (Fig. lb.) A binucleate condition of 

 the cells below this layer becomes apparent, probably arising 

 from the absorption of the cell wall between two contiguous 

 vegetative cells. (Fig. i b, c, and Fig. 3.) 



The binucleate teleutospore mother cell gives rise, by a process 

 of conjugate division, to the teleutospore cell, and a stalk cell. 

 The former swells and at first contains two nuclei ; these latter 

 fuse, and the teleutospore ultimately assumes its mature form. 



(Pig- 5-) 



Telentosporcs. — P. Magnus figures a teleutospore from Aloe 



maculata; he showed the presence of very minute outgrowths on 



the epispore, a structure which had been missed by both Cooke 



and Hennings. There is a certain amount of difiference between 



the spores obtained from Uromyces Aloes growing on Aloe 



arborescens, and those from Uromyces Aloes on other species 



% 



Fig. 5- 



of Aloe, e.g., A. Transvaalensis. Dimensions of spore from Aloe 

 Transvaalensis are 20 X 30 /x. Dimensions of spore from Aloe 

 arborescens, 19 X 20 yu, ; the latter is thus smaller, and is a shade 

 lighter in colour. (Fig. 6 a and b.) 



Germination takes place best at room temperature. Spores 

 from Aloe Transvaalensis show good germination in distilled 

 water after eight hours, a goodly proportion having formed germ 

 tubes of about three spore lengths long. (Fig. 6 c.) Whereas 

 spores from Uromyces on Aloe arborescens, after similar treat- 

 ment, show no germination, though germination after 24 hours is 

 good. Moreover, the germ tube or basidium is narrower and 

 has an invariable tendency to coil. (Fig. 6 (/.) 



The distal end of the basidium receives the cell contents, 

 and divides to form as a rule four cells, the basidiospores ; there 

 appears to be a certain amount of variation in the order of origin 

 of these four cells, as can be seen from the Fig. 6 e and /. Each 

 of the basidiospores may give rise to a delicate germ tube. I have 

 been unable to notice the formation of sporidia, nor have I been 

 able to obtain their formation experimentally. In water 

 with abundant supply of air the germ tubes grow until their 



