CHAP. V. COMPARATIVE REVIEW. -ASCOMYCETES. ERYSIPHEAE. 2O1 



and in Pleospora and Nectria the paraphyses are even formed from the same group. 

 Hartig's conjecture with regard to Nectria may certainly hold good of Claviceps and 

 also of Epichloe, that special ascogenous initial organs are really present on the 

 very young stroma, but up to the present time have been overlooked; as regards 

 Pleospora we have only Bauke's somewhat imperfect preliminary communication. 

 With the accounts at present before us our knowledge is limited to the alleged 

 mode of differentiation. If we choose to speak of ascogonium or archicarp in 

 these genera, we must apply the term only to the initial organs which are late in. 

 forming and not very distinct in their differentiation. Van Tieghem's discomycetous 

 genus Ascodesmis would belong to this series, if that writer's not very complete 

 account of it is correct. 



We now proceed to give the details which are necessary for the full under- 

 standing of what has been said above, and to add some supplementary observations. 

 The arrangement of the material is for perspicuity's sake somewhat different from 

 that adopted in the foregoing account. 



K 



FIG. 93. Podosphaera Castagtttf on Taraxacum. Development of the sporocarp. Stages of the development according to the 

 letters FN. o superior, inferior mycelial filament, a antheridial branch, / archicarp. In (7 the envelope is beginning to form, in H 

 the outer wall is complete. K a young sporocarp quite transparent. N a similar one in optical longitudinal section ; s an ascus, r the 

 outer wall, i the cells of the inner wall formed from the outer. Magn. 390 times. 



SECTION LXIV. i. Erysipheae (Fig. 93; see also Fig. 107). The mycelium 

 of these epiphytic parasites is composed of branched septate hyphae which spread 

 over the surface of the host, being attached to its epidermis by the haustoria 

 described in section V, and frequently touch and cross one another. The formation 

 of a sporocarp begins at the point of contact or crossing of two branches. The 

 process is of the simplest kind in Podosphaera. Two branches put out short 

 protuberances at the same time, which rise erect from the surface of the epidermis 

 and are soon delimited by a transverse wall. The one which proceeds from the 

 lower of the two branches where they cross takes the form of an elongated ellipsoid 

 cell, 2-3 times the length of the transverse diameter of the parent-branch, and is 

 the archicarp. The other, the antheridial branch, remains cylindrical in shape, 

 being of the same breadth as the mycelial hypha from which it springs or a little 

 narrower; it is always closely applied to the archicarp, and its upper extremity 



