CHAPTER V. — COMPARATIVE REVIEW. — ASCOMYCETES. 197 



hyphae closely united together. It bears at its apex the spherical spore-receptacle 

 which is about 2 mm. in diameter and has its dense hyphal weft differentiated into a 

 wall or peridium composed of many layers of an unevenly floccose loose pseudo- 

 parenchyma, and a spore-forming gleba within the peridium. The general form of the 

 gleba is that of a flattened sphere ; it consists of closely interwoven and very copiously 

 branched hyphae, which produce everywhere countless asci in dense tufts on the 

 extremities of their branches. The asci are comparatively small ovoid bodies 

 containing each eight delicate ellipsoid spores, which are released when ripe by the 

 disappearance of the membrane of the ascus. When the entire mass of spores is ripe, the 

 whole structure dries up, the peridium opens by a circular fissure and becomes detached 

 like a cap, and the cinnamon-coloured spores are scattered like dust from the flocculent 

 remains of the ascogenous hyphae. Onygena equina, P. a more robust form has, 

 according to Tulasne, a precisely similar structure. 



4. Myriangium Durieui grows on the rind of trees and forms a large, flat, black 

 thallus from one to a few millimetres in size composed of a tolerably uniform narrow- 

 celled pseudo-parenchyma with brown cell-walls. The sporocarps are protuberances on 

 the outside of the thallus, and consist, as we know from Millardet's researches, of a 

 pseudo-parenchyma similar to that of the thallus, but of finer texture, between the cells 

 of which spherical asci are everywhere distributed usually at some distance from 

 one another. The sporocarp thus constituted occupies the middle of a round 

 protuberance of the thallus in the earliest stages that have been examined. It then 

 grows by constant formation of new cells in a meristematic tissue which lies on its 

 inner side, the side which is turned to the substratum. From this tissue new layers of 

 ascogenous parenchyma are thrust one after another towards the outside. In conse- 

 quence of the pressure thus produced the original tissue of the thallus in this part is rup- 

 tured, and the exposed ascogenous tissue breaks away as new tissue is pushed forward. 

 The great capacity for swelling in the membranes of the ripe asci in the older tissue-layers 

 favours their removal. The youngest asci lie near the layer of meristem between the cells 

 of the pseudo-parenchyma, from which they are chiefly distinguished by their greater 

 abundance of protoplasm. As they move towards the outside they grow to 8-10 times 

 their original diameter and produce eight pericellular compound spores ; the germina- 

 tion of the spores is as little known as the further details of their development. 



Origin of the Sporocarp. 



Section LXIII. The first steps in the formation of the sporocarp (fruc- 

 tification) of the Ascomycetes have up to the present time been closely studied in 

 comparatively few species; the search for and clear preparation of the first com- 

 mencements is in most cases difficult from the small size of the objects, and there is 

 difficulty also in unravelling the hyphal weft. The subject has been investigated in 

 a certain number of species in all the chief divisions of the group, and important 

 differences, recurring in all cases in their most essential points, are found to exist even 

 between species which resemble each other very closely in the more advanced state. 

 Intermediate forms are found between the several cases which differ extremely from 

 one another. The whole series may be arranged in the following order. 



1. Eremaseus albus is the name given by Eidam to a small Mould which may 

 be cultivated in nutrient solutions, and which has a filiform septate many-celled 

 mycelium. To form the sporocarp (Fig. 92) two adjoining cells of the mycelium 

 put out each a lateral branch (a) close by the transverse wall which divides them. 

 The two branches are from the first in contact with one another ; they are exactly 

 alike, and they grow coiling spirally round one another to a length exceeding the 



