CHAPTER V. — COMPARATIVE REVIEW. — ASCOMYCETES. — EVROTIUM. 203 



divides by transverse walls into a row of several cells, from which a number of 

 broadly club-shaped erect asci are formed by each cell of the row growing out 

 directly into an ascus, or putting out a few short branches which terminate in asci 

 and are therefore ascogenous. 



In both Erysiphe and Podosphaera the formation of the envelope is at first in 

 advance of that of the asci, and is nearly finished when the asci or the cells which 

 produce them are still quite small, and it is not till the last stage of the development 

 that the growth of the asci advances, chiefly at the expense of the tissue immediately 



FIG. 94. Eurotium repens. A branch of the mycelium with a gonidiophore c and young archicarps as : si sterig- 

 mata. B spirally twisted archicarp as with the antheridial-branch/ and an envelope-branch. C older specimen with a 

 larger number of envelope-branches growing round the archicarp ; p antheridial branch. D young sporocarps seen from 

 without. E and F other young sporocarps in optical longitudinal section. I n E the inner wall is beginning to be formed ; 

 ■w the outer wall, / the inner wall-cells and the cells filling the space between the ascogonium and the wall, as the 

 ascogonium. G ascus with spores, //ripe ascospore of E. Aspergillus glaums isolated. A magn. 190 times, the rest 

 of the figures 600 times. 



surrounding it. The spores are in most cases formed as soon as the asci have 

 reached their full size ; but in some species, as Erysiphe Galeopsidis and E. graminis, 

 (Wolff), there is a pause in the development before the formation of the spores, and 

 further progress only takes place under favourable conditions of temperature and 

 moisture after a resting period of some duration which happens to fall in the winter- 

 time ; the protoplasm of the tissue of the inner wall is evidently employed to form 

 the spores. 



2. The archicarp of Eurotium (Fig. 94) is produced by the gradual basi- 

 petal coiling of the extremity of the upper end of a branch of the mycelium into 



