ONION SMUT FUNGUS. 101 



The follo-fting species can be scrmiiiated in water as soon as mature: 

 Cintractia densa McAlp. (11); C. Sorghi vulgaris (Tul.) Clint., 12 hours, ^ 

 (11); Enlyloma canescens (14); Schizonella melanogramma D. C. (4); 

 Sorosporium Reiliantim (Kiilm) McAlp., tap water, 17 hours (11); Tillctia 

 zonata Bref. (4); Urocysfis occulta Wallr. (11); U. primulicola Magn., 10 

 hours (14); U. Violac Sow. 5 days (4); Ustilngo Avcnae (Pers.) Jens., 6 to 

 8 hours (8), (11) and others; U. Boutclonae humiilis Bref. (4); U. Carho 

 Tul., 6 to 10 hours (5); U. flosculorum, 5 to 6 hours (7) (he finds that 

 fresh spores germinate most quickly); U. grandis Fr., 24 hours (3); U. 

 longissi7na Sow., 3 to 4 hours (3), (7) ; U. major 24 hours (14) ; U. Panici 

 glauci Wallr., 8 daj^s (3); U. Readeri Syd. (11); U. segetum, 6 to 8 hours, 

 "fresh spores germinate better" (14); Ust. violacea Pers. (3) and many 

 others. In the most favorable cases germination begins within two to 

 three hours, while at the other extreme McAlpine (11) mentions species 

 the spores of which did not begin to germinate until they had been in water 

 for several weeks. Where such extreme lengths of time are required, the 

 question arises as to whether this is not really the time required for the 

 weathering process such as takes place when they are kept in damp soil, 

 as in Bref eld's experiments. 



Air. — Some spores require only a moist air for germination, and will 

 not germinate at all or only abnormally when immersed in water. Thus 

 Fischer von Waldheim (7) writes : — 



For the normal germination of the different species of Ustilago, a certain quantity 

 of water or moisture is usually necessary. For this purpose, the spores need only 

 be placed in a drop of water, or upon moistened earth, or even merely in an atmos- 

 phere kept moist; for instance, under a glass globe placed over a dish of water. 

 But Tilletia and Urocystis germinate only in damp air (for instance, under the 

 glass globe mentioned) , and their germinating spores, coming in contact with water, 

 only show abnormal appearances. 



In Brefeld's germinating apparatus the spores were never entirely im- 

 mersed in water, but in the thin film clinging to the chamber walls must 

 have always had a sufficient quantity of air. This probably contributed 

 to his remarkable success in germinating the spores of a very large number 

 of species. McAlpine also found that he was able to secure germination 

 in many cases only by floating the spores in a watch glass over water. 

 Both Brefeld (3) and Fischer von Waldheim (7) mention the fact that the 

 spores of Tilletia caries germinate in damp air. Plowright (14) had a 

 similar experience with Tubercinia trientalis. McAlpine (11) was able to 

 germinate the spores of Tillctia Tritici (Bjerk) Wint. best by keeping them 

 on moist filter paper or blocks of plaster of Paris kept moist by capillary 

 water from a dish in which the blocks were partially immersed. He (11) 

 makes the following interesting observation on the necessity of air for 

 germination of spores of Ustilago Readeri Syd.: • — 



' Figures after the species and not in parentheses indicate the time required for germination to 

 begin after the spores were placed in water. Omission of them indicates that the investigator 

 gave no data as to time required. Numbers in parentheses refer to bibliography on pp. 132 and 

 133. 



