54 TEXT-BOOK OF FUNGI 



spore. In Eremasats and Dipodascus there is no trace of 

 epiplasm in the ascus. 



The oospore is formed as follows : The oosphere is 

 differentiated owing to a concentration of protoplasm in 

 the central portion of the oogonium. The primitive wall 

 of the oospore is formed immediately after fertilisation ; 

 afterwards the epispore is formed from the periplasm, or 

 portion of protoplasm in the oogonium left outside the 

 oospore. In some instances the wall of the oogonium 

 also remains, and forms an additional protective covering 

 to the oospore. The wall of the mature oospore is thick, 

 and usually stratified. 



Zygospores are formed by the union of two gametes ; 

 when these meet, each gamete replete with cytoplasm is 

 cut off from its supporting hypha by a cross-wall ; the 

 double wall, where the two gametes join each other, is 

 absorbed, and the contents of the gametes mingle to form 

 a zygospore. When the union of the gametes is complete, 

 thickening and cuticularisation of the epispore commences 

 from a circular zone corresponding to the original line of 

 union of the two gametes. 



In the Saccharomycetes, or Yeasts, three modes of spore- 

 formation are known, i. By budding, a purely vegetative 

 form of reproduction. When conditions of growth are 

 favourable, a yeast-cell, which constitutes an individual, 

 puts out a bud or swelling from any part of its surface. 

 This bud continues to increase in size, being attached to 

 its parent cell by a narrow neck across which a septum is 

 formed, and finally becomes free. When growth is very 

 vigorous, a cell may produce two or more buds or daughter- 

 cells from different parts of its surface. These daughter- 

 cells may in turn produce other buds, so that short chains 



