EU-MYCETES. 



ASCOMYCETES 



437 



wliich 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, 

 rt, 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 oft' at the time of ripening of the grain. 

 They are the commercial source of suppK' 

 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. 



Morchdla csculcnta, the fraitiii;^ 

 body of the Morel. The convo- 

 luted folds of surface are covered 

 by the hyinenial layer, bearing' 

 asci. (* nat, size.) (.\fter Stras- 

 bui'ger.) 



d 



1 



Fig. 371. 

 Tuber riifiim : a Truffle. The fructification in vertical section ( :■ 5). a = cortcx. 

 (7 = dark veins of compact hypbae. d= air-containing tissue, h = ascogeuous hx-phae, 

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



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

 of the resting sclerotium. 



