REPRODUCTION. 199 



known as sclerotium in its resting stage. This plant has potent 

 medicinal properties. In its general outline the sclerotium takes 

 on the form of the rye-grain which it attacks ; it is usually larger 

 and somewhat curved. It consists of a closely woven network of 

 hyphal filaments (mycelium) forming a firm semi-cortical structure, 

 brown externally and white internally. Infection takes place as fol- 

 lows : The surface of the young rye-ovary is covered by a mycelial 

 network (honey-dew) which also penetrates the interior. Conidia 

 are formed on the exterior. This conidia-forming network was 

 formerly known as Sphacelium, and was supposed to be a dis- 

 tinct fungus. Near the base of this structure the mycelium of the 

 sclerotium begins to form ; this develops rapidly and in its mature 

 state bears the remnants of the sphacelium and the rye- ovary on 

 its apex. The sclerotium is a " pseudo -parenchyma," that is, the 

 hyplise of the fungus are so closely interwoven that they resemble 

 a parenchymatous tissue. (Such pseudo-parenchymatous tissues are 

 also met with among lichens.) The conidia, which are formed 

 when the rye is in blossom, constitute the first means of propagation 

 and spreading from seed to seed. The sclerotium, which lies 

 dormant during the winter months, develops elongated spores in 

 the spring. These spores (ascospores) constitute the second form 

 of reproductive cells of this fungus. Under favorable conditions 

 the ascospores may develop in the fall, but the sclerotinm is specially 

 adapted to withstand the vicissitudes of the winter season, so that 

 its spores may develop into the sphacelium -stage during the follow- 

 ing spring. Preventative measures : Since this fungus is in great 

 demand by druggists (even imported from America), it will pay 

 doubly to collect the sclerotia before the grain ripens. 1 In the 

 second place non-infected seed-grain must be selected. It is also 

 well to destroy such grasses as Lolium perenne, which frequently 

 spreads the fungous disease. 



Reproduction among lichens 2 is the same as in that group of 

 fungi which constitutes the fungal symbiont in the lichen-structure. 

 In the great majority of lichens the fungal portion is derived from 

 the Aseomycetes, a few genera from the Basidiomycetes. They 

 also reproduce by means of vegetative organs, the soredia, which 



1 It might be mentioned that such a procedure would scarcely be successful 

 in the large grain-fields of America. TRANS. 



2 Their structure was briefly discussed under Symbiosis. 



