EU-MYCETES. (a) ASCOMYCETES 



437 



which causes a disease on Rye-crops. The fungus attacks the ovaries 

 of the Rye and other Grasses at the flowering period, spreading over 

 them and causing the condition known as 

 " Honey-Dew." This is the conidial stage, 

 and it is spread from plant to plant by 

 insects, which are attracted by a sugary 

 secretion in which the conidia float (Fig. 369, 

 a, b ; also Fig. 341, p. 406). But the effect 

 becomes more apparent as the crop ripens, 

 for in place of the normal grains long curved 

 bodies project from the ear (Fig. 369, c). 

 These are the sclerotia of the fungus, which 

 fall off at the time of ripening of the grain. 

 They are the commercial source of supply 

 of a useful drug. In this resting stage the 

 winter is passed. In spring the sclerotia 

 germinate, forming numerous pinhead-like 

 growths, which bear the flask-shaped peri- 

 thecia characteristic of the large group of the 

 Pyrenomycetes (Fig. 369, d, e). Finally in 

 these the asci and thread-like ascospores 

 are matured at about the time when the 

 Grasses flower. It has been proved . experi- 

 mentally that hyphae from the germinating spores invade the Grass- 

 flowers, causing the development of the conidial stage again. The 



FIG. 370. 



Morchella esculenta, the fruiting 

 body of the Morel. The convo- 

 luted folds of surface are covered 

 by the hymenial layer, bearing 

 asci. (f nat. size.) (After Stras- 

 burger.) 



FIG. 371. 



Tuber rufum : a Truffle. The fructification in vertical section ( x 5). a = cortex. 

 c = dark veins of compact hyphae. d = air-containing tissue, h = ascogenous hyphae, 

 with numerous asci. (After Tulasne ; from Strasburger.) 



life-history is here essentially the same as before, but with the addition 

 of the resting sclerotium. 



