398 MXPEBIMENTS WITH PLANTS 



discharge a perfect cloud of black spores. If we 

 investigate these masses before they have grown to 

 the size of a pea we find a mass of mycelium, similar, 

 in a general way, to that of the Bread Mould; later on 

 this mycelium forms spores by breaking up into its 

 constituent cells, which separate from each other, each 

 cell becoming a spore. The spores are scattered by the 

 wind and germinate in the soil or wherever they can 

 find moisture and suitable food. Germination may 

 take place at once or may occur the following season. 

 In order to see the germination of the spores, we may 

 cultivate them in a hanging drop of steril- 

 ized dung liquor, sterilized plum juice (made 

 by stewing prunes in water and just neutral- 

 izing the acid by adding ammonia water) , 

 Pasteur's solution ^ with sugar or in modified 

 Cohn's solution. 2 



The spore first puts out a germ-tube (Fig. 

 222) ; when this has become several cells, 

 long elongated spores make their appearance 

 (Fig. 223, (•) ; these are called conidia. They develop 

 much more abundantly in contact with air (i. e., on the 

 surface of the liquid). It is the conidia which infect 



1 This can be made up by a druggist as follows : Monobasic - potassium 

 phosphate, 20 parts; tribasio calcium phosphate, 2 parts; magnesium sulphate, 

 2 parts ; ammonium tartrate, 100 parts; cane-sugar, 1,500 parts; water, 8,57G 

 parts. 



2 This may be made up by a druggist as follows -. Distilled water, 42.3S5 

 grams ; cane-sugar, 7 grams ; ammonium tartrate, .250 grams ; potassium 

 phosphate, .125 grams; magnesium sulphate, ,125 grams; calcium phosphate, 

 .125 grams. 



