302 



Journal of Agricultural Research 



Vol. XIII, No. 5 



SPORE GERMINATION 



To observe spore germination, Van Tieghem ceiis and slides supported 

 in petri dishes were used. In the latter case drops of liquid containing 

 the spores were placed directly on the slide. The spores were scraped 

 from the surface of the culture or leaf and filtered through fine silk bolt- 

 ing cloth to separate them from each other, and they were then dropped 



on the slides. With 

 the Van Tieghem cells 

 the spores were trans- 

 ferred directly to the 

 covers from cultures. 

 The first signs of 

 germination consist in 

 a slight swelling of the 

 spore owing to in- 

 creased turgidity. In 

 from three to six hours 

 some of the cells were 

 observed to have a 

 slight protuberance, 

 the beginning of the 

 germ tube (fig. 2, A, F). 

 Two hours later the 

 germ tube was found 

 to have pushed out 5 to 

 10 mm. (fig. 2, B, G). 

 In beef bouillon or 

 other nutrient bouillon 

 the growth is fairly 

 rapid from now on. 

 In fig. 2, A-E, is shown 

 a spore in various 

 stages of germination. 

 Not all of the cells 

 germinate, but in the 

 case of large spores the writer has observed as many as a dozen germ 

 tubes. Only one germ tube is produced from a single cell. The germ 

 tubes branch profusely and soon become septate (Pi. 24, A; fig. 2, E, H). 

 "Within 72 hours they have frequently become a tangled mass of threads. 

 Fusions of the hyphse are quite common (fig. 3). 



In water, germination is slower, and growth soon ceases. Frequently 

 vesicular, highly vacuolate, thin-walled bodies are produced (fig. 2, I, J). 

 These may break away, or a germ tube may grow from them while still 

 attached to the original germ tube. They probably have no significance 

 in the life history of the organism. 



Fig. 1. — Spore formation of Slemphylium cucurbilacearum (Material 

 taken from striug-bean-agar cultures 12 days old. Xi,o5o): A, B, 

 earliest stages of spore formation, showin g origin of conidiophores on 

 mycelium; C-F, early stages in spore formation, showing the trans- 

 verse divisions of the conidiophores; G-N , various stages in the 

 maturation of the spores. 



