368 



THALLOPHYTES 



numerous nuclei of the antheridium flow into the trichogyne and 

 pass on into the oogonium where they pair and fuse with the 

 numerous nuclei of the oogonium. From the fertilized oogonium, 

 now known as the ascogonium, branches called ascogenous hyphae 

 are developed and on the ultimate branches of these are produced 



the asci. From beneath the 

 ascogonium sterile hyphae 

 (hyphae producing no asci) 

 grow up among the ascoge- 

 nous hyphae and constitute the 

 paraphyses of the hymenium. 

 Other sterile hyphae form the 

 wall of the cup-shaped plant 

 body or ascocarp. Usually 

 several oogonia are involved 

 in the formation of a single 

 ascocarp. 



Brown Rot of Stone Fruits 

 (Sclerotinia fructigena). — 

 This Fungus, shown in Figure 

 319, is one of the parasitic 

 forms of the Pezizales. In 

 some years this Fungus is an 

 extremely destructive para- 

 site. It attacks nearly all 

 stone fruits and in some years 

 nearly half of the Plum and 

 Peach crop may be destroyed 

 by this disease. In Georgia 

 the estimated loss in Peaches 

 and Plums caused by this 

 disease in 1900 was between 

 $500,000 and $700,000. To a 

 limited extent it attacks the twigs and flowers and does some 

 damage in this way. 



Fruits half size or larger seem to be most susceptible to the 

 attack of the Fungus. The disease first shows as small decayed 

 spots, dark brown in color. The fruit decays rapidly and soon 

 hyphae break through from beneath, forming moldy patches on 

 the surface. The moldy patches contain conidiophores which 



Fig. 319. — Sclerotinia fructigena. 

 Above, the apothecia developed on a 

 decayed Plum; at the right, below, 

 section through an apothecium, show- 

 ing asci and paraphyses; at the left, 

 below, an ascus and paraphysis more 

 highly magnified. After Duggar. 



