CHAP. V.—COMPARATIVE REVIEW.—-ASCOMYCETES.—ERYSIPHEAE. 201 
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. 


FIG. 93. Podosphaera Castagnei on Ti D of the sporocarp. Stages of the development according to the 
letters Z—N. o superior, # inferior mycelial filament, a antheridial branch, g archicarp. In G the envelope is beginning to form, in 4 

the outer wall is Ka young P quite N a similar one in optical longitudinal section; s an ascus, 7 the 
outer wall, 7 the cells of the inner wall formed from the outer. Magn. 390 times. 

Section LXIV. 1. 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 
