i68 



Bulletin 395 



condition, surrounded by the remainder of the ascocarp, give the appear- 

 ance of one of the true discomycetes. This, however, is brought about by 

 the persistency of the outer cells of the shield-like layer which covers the 

 immature ascocarp. In the presence of sufficient moisture the exposed 

 asci elongate to approximately three times their usual length. This 

 process is very rapid and may be observed under a microscope when a 

 fragment of tissue containing asci is placed in a drop of water. The lower 

 part of the ascus remains fastened in the cavity in which it was borne, 

 giving a conical shape to the body which raises itself above the surrounding 

 tissue. The spores gather at the tip of the ascus and from there are ejected 

 into the air. They have been caught at a distance of one centimeter above 



the lesions. 



Even in a single asco- 

 carp all the asci are never 

 of the same age, and the 

 ascocarp s on the same 

 cane seem to vary in this 

 respect. In 191 5 mature 

 ascospores were first ob- 

 served about the first of 

 June, while other asco- 

 spores were not mature 

 until later in the summer. 

 The ascospores, like the 

 conidia, have walls which 

 are very gelatinous and 

 stick>^ and great difficulty 

 was experienced in tr^nng 

 to pick up single spores by 

 means of a glass tube, as 

 described by Barber.^ The spores adhere especially to the glass slides, 

 and it was impossible to get them into the bore of the tube. Single asci, 

 however, could be separated in this manner. 



When placed in tap, rain, or distilled water, or on nutrient agar, the 

 mature ascospores germinate very readily. They swell somewhat, and 

 within less than two hours a short sterigma is produced from one or each 

 of the cells. A sprout conidium is formed, which is from oblong to ellip- 

 tical in shape and is identical with the conidia of the fungus borne in the 

 acervuli (fig. 17). When fully mature the sprout conidia drop from the 

 sterigmata but they do not germinate immediately. After a short period 

 of rest, from twelve to twenty-four hours, a germ tube is developed and 



" Barber, Marshall A. On heredity in certain microorganisms. Kansas Univ. sci. bul. 4-3-48 1907 



278 



Fig. 17. ASCOSPORES of plectodiscella veneta 



Showing various stages in the formation of the sprout conidia. 



X 1132 



