THALLOPHYTA. 



681 



Pyrenomycete which produces an antler-like stroma resembling that of Cordyceps 

 Taylori, and which is exceedingly common on old tree stumps, is Xylaria 

 Hypoxylon. Indeed, the stroma represented in fig. 385 * would almost do for that 

 of this Xylaria. It is purplish in colour below where the perithecia are borne; at 

 the tips it passes over into a glaucous grey colour, this bloom being due to the 

 conidia, which are abstricted in this region. Another curious fingered species, X. 

 polymorpha, is also met with in similar situations. Claviceps purpurea, the Ergot 



Fig. 387. Various Ascomycetes. 



a Section through part of a Truffle (Tuber melanosporur*) showing a portion of the cortex (below) and a chamber containing 

 oval asci, each of which contains 4 spores. 2 Vertical section of the apothecium of a discomycetous Lichen, Physcia 

 ziliaris (after Sachs). The Yeast-plant, Sacclvtromyces cerevisece. *, 6 , Single Yeast-cells showing development of a 

 sprout. 1 A cell containing two spores. 1 x 200 ; 2 x 60 ; x 600 ; -r x 1000. (Partly after Rees. ) 



of Rye and other grasses, is a very interesting form. The spores attack the ovaries 

 of Grasses and invest them with a mycelium from which conidia are abstricted in 

 large numbers (fig. 386 2 ). These can at once infect new plants. Gradually the 

 whole ovary is replaced by a mass of fungal substance, the sclerotium. In the 

 autumn at the time of harvest the ears of Rye may be seen with these dark 

 sclerotia projecting from them (fig. 386 x ). Care has to be exercised that they do 

 not get mixed up with the grain, as the Ergot contains an alkaloid and other 

 poisonous substances, and if intermingled with food causes a disease which has 

 received the name of ergotism. The sclerotia remain dormant through the winter. 



