PEZIZALES 



321 



sitic families, the Mollisiaceae and Helotiaceae, and the saprophytic 

 Geoglossaceae. In the Mollisiaceae and Helotiaceae the peripheral layers 

 are developed to a special peridium; in the Geoglossaceae the hypothe- 

 cium is homogeneous but differentiated into pileus and stipe; in the 

 Mollisiaceae the peridium is paraplectenchymatic and often built of 

 dark, thick-walled cells; in the Helotiaceae it is prosenchymatic and 

 formed of hyaline, thin-walled cells. 



Fig. 212. — Pseudopeziza Ribis, a, with its secondary spore form, Gloeosporium Ribis, b. 



(After Klebahn, 1906.) 



Mollisiaceae. — Pseudopeziza (Drepanopeziza) Ribis (Klebahn, 1906), 

 causing anthracnose of Ribes rubrum and R. aureum, from early summer 

 on, produces small brown conidial spots singly or in fused groups 1 or 2 

 mm. broad, which arise under the upper epidermis of leaves and subse- 

 quently raise and rupture it (Fig. 212, 6). They were earlier described 

 as Gloeosporium Ribis. Their spores are colorless, unicellular and sickle 

 shaped, with the thickest spot toward one end rather than in the middle. 

 In damp weather they swell out as light-brown, waxy columns and are 

 generally scattered by rain or insects. They retain their ability to germi- 

 nate, and possibly to infect, over the whole winter. During the winter, 



