CHAPTER V.—COMPARATIVE REVIEW.—ASCOMYCETES. 247 
described above on page 229, in the case of Pleospora; an intercalary portion of a 
mycelial filament grows by successive divisions which arise without fixed order in 
every direction, and the cells thus formed are subsequently differentiated, while branches 
from adjoining hyphae usually grow up round the new body and thus help to form its 
wall (see Fig. 118). This is the mode of formation according to Gibelli and Griffini, 
Eidam and Bauke not only in Pleospora herbarum, but also in Cucurbitaria elongata, 
Leptosphaeria doliolum and two other species not precisely determined, and according 


5 
FIG. 118. Pleospora Alternariae, Gibelli. (Determination not certain FIG. 119. Cicinnobolus Cesatii (De Bary, Beitr. III), para- 
from the absence of perithecia.) Young stage of development of pycnidia. sitic on Erysiphe. Aripe pycnidium (seen from without) 
a of the ing and rapid transverse division of the open above on the left and discharging its sporess, having de- 
intercalary portion of a hypha, which is developing into a pycnidium and veloped in a gonidiophore of the Exysiphe which is attached 
has branches from itself and from an adjacent hypha attached to it. tothe mycelial filament x x and bears four dead gonidia ¢ on 
6 older stage of the development. The mature structure of these pycnidia itssummit. 2asmallandnearly ripe pycnidium, formedona 
closely resembles that represented in Fig. 119, only the wall is formed of branch of a mycelial hypha 2 m of the Erysiphe, in which 
several layers, Magn. 600 times. the slender mycelial hyphae of the Crciznobolus may be 
seen. The figure shows the upper surface and the optical 
longitudinal section of thet ent peridium ; the section 

shows the young spores growing inwards from the one- 
layered wall. C tranverse section through the wall of a ripe 
pycnidium with three primordial spores sprouting inwards. 
D two ripe spores just di: d from the pycnidium and 
a germinating spore. 4 magn. 380, 5, C 600, D 300 times, 

to Zopfin some pycnidia of Fumago ; Brefeld’s ‘Pycnis sclerotivora’ must also be added 
to the number. Other pycnidia are not meristogenetic but symphyogenetic formations, 
that is, they are produced by union and interweaving of hyphal branches; such are 
those known under the name of Cicinnobolus, some in the genus Fumago, and 
the Diplodia-form examined by Bauke. The formation of the pycnidia in Pleospora 
polytricha, according to Bauke, is of an intermediate kind, the inner portion being 
meristogenetic and the numerous outer wall-layers symphyogenetic. The structure of 
pycnidia formed in these different ways may be quite alike in the matured state, as is 
seen by comparing Cicinnobolus (Fig. 119) and Pleospora. 
