302 



PART III. THE CLASSIFICATION OF PLANTS. 



Among the simple forms with free perithecia may be mentioned the genera 

 Chsetomium ; Sordaria ; Trichosphaeria ; Sphserella, many species of which 

 appear on dead leaves as black spots ; Calosphaeria, which forms its long 

 slender perithecia in groups on the wood and bark of cherry-trees (C. Princeps) ; 

 Pleospora ; Massaria ; etc. 



In the compound forms, those, that is, which have a stroma, the stroma 

 forms warty incrustations or patches of irregular outline, which have a punct- 

 ated appearance owing to the numerous openings of the perithecia : Diatrype 



C 



FIG. 212. Claviceps purpurea. A A sclerotium (c) bearing stromata (x 2). B Section 

 of a stroma; cp the perithecia. C A peritheciam more highly magnified. D An ascus 

 ruptured ; the elongated spores (sji) are escaping. (After Sachs.) 



disciformis, which forms black warts as large as peas, belongs to this group, it 

 is very common on dead boughs ; also Nectria cinnabarina, which has a bright 

 red stroma, and occurs on many kinds of dead wood ; Nectria ditissima causes 

 a disease on the branches of Beech-trees. In other cases the stroma developes 

 into an upright club-shaped or branched tufted body, like the stromata of 

 Xylaria, for instance, which occur very frequently on the trunks of trees; of 

 Cordyceps, which grow from the bodies of insects ; of Claviceps, which spring 

 from the Ergot-sclerotium (see p. 295). In most forms, the stroma bears a 

 crop of gonidia before it developes the perithecia. 



Order III. Discomycetes : the ascocarp is an apothecium of various form ; 

 a stroma sometimes present. 



The order may be divided, according to the form of the apothecium, into the 



