102 



PYRENOMYCETES 



[CH. 



Leptosphaeria includes some 500 species characterized by the papillate 

 or conical ostiole, usually free from hairs. The majority are saprophytes on 

 plant remains, some are parasites on land plants, and some on the Red 

 Algae. 



L. Lemaneae occurs on the thalliis of various species oi Lemanea {?ig. 121). 

 The mycelium consists of uninucleate cells and ramifies in the intercellular 

 spaces of the host, sending branched haustoria into the cells. Here and there 

 the hyphae are dilated (fig. 122 a, b), and in these regions show denser and 

 more refractive contents than usual. Fusion takes place between the dilated 

 portions (fig. 122 c, d) which may be terminal or intercalary, and there is 



P'ig. 121. Leplosphacria Lemaneae (Cohn) 

 Brierley ; transverse section through thal- 

 lus of Lenianea, showing perithecium, 

 X 125 ; after Brierley. 



Fig. 122. Leptosphaeria Le- 

 maneae (Cohn) Brierley ; 

 a. b. (.. d. stages of fusion 

 between dilated hyphae ; 

 after Brierley. 



evidence that the nucleus of one of the swollen cells passes across into the 

 other, which may therefore be termed the oogonium, and fuses with its 

 nucleus. The oogonium then divides to form a ■ number of multinucleate 

 cells from which ascogenous hyphae arise. The nuclei in these hyphae are 

 paired and the usual fusion takes place in the ascus. From the cells adjoining 

 the oogonium the delicate hyphae of the sheath grow up. The morphology 

 of the sexual organs in this genus is quite unusual, but they may perhaps 

 best be compared with the dilated cell observed by -Dangeard in the initiation 

 of the perithecium in Sporormia intermedia; in that case, however, there 

 does not appear to be a functional antheridium, and vegetative cells as 

 well as ascogenous hyphae are stated to develop from the initial cell ; the 

 resemblance demands further investigation. 



