INTRODUCTION TO CRYFTOGAMIC BOTANY. 283 



these stylospores, conidia are frequent on the mycelium. Haplo- 

 sporium, Mont., which grows upon bulbs in North Africa, is 

 remarkable for containing only a single sporidium in each ascus. 

 Sphceria Posidoniw grows on the African coast, on the roots 

 of Posidonia, where it is constantly subject to the action of 

 salt water ; and S. herbarum, which affects plants of widely 

 different genera, has been found on decaying seaweeds. 



291. Thainnomyces is remarkable for the extremely slender 

 forms assumed by the stroma in many species, in some of 

 which it is very brittle, and in one curiously annulated. Most 

 of them are tropical species ; but one is not uncommon in this 

 country, on decaying mats made of Scirpus lacustris or on 

 hemp sacs. In those species which I have examined, there is 

 no true perithecium, and the asci are more rapidly absorbed 

 than in normal Sphceriacei. In Micropeltis the perithecium 

 is extremely flat, and the asci all radiate from a central point. 

 The species are tropical, but are represented in temperate 

 countries by species of Microthyrium, which perhaps is not 

 sufficiently distinct as a genus. The whole tribe yields scarcely 

 a jilant of any utility. Hypoxylon vernicosum is a bad 

 article of food, and Cordyceps sinensis a drug of doubtful 

 virtues. Their great end seems to be the decomposition of 

 hard tissues and the nourishment of thousands of insects. 



4. Phacidiacei, Fr. 



Hymeniam at length more or less exposed ; disc orbicular 

 or linear ; margin generally involute ; walls coriaceous. 



292. The foregoing division was distinguished by its more or 

 less spherical perithecia, assuming sometimes a compressed out- 

 line, from lateral pressure either of the fibres of the matrix, or 

 of neighbouring individuals crowding in upon each other, but 

 by no means deviating normally. The aperture was for the most 

 part minute and circular, or, if linear from their characteristic 

 form, it was very short, and arose from the compression of the 

 orifice. We have here, on the contrary, highly elongated and 

 even branched perithecia, or where the normal form is cii'cular 

 it is in general rather orbicular than spherical, in conse- 

 quence of the widely expanded aperture exposing the hyme- 

 nial surface to tlie action of light, insomuch that it assumes 



