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. 1 1 8). This is the mode of formation according to Gibelli and Grifnni, 

 Eidam and Bauke not only in Pleospora herbarum, but also in Cucurbitaria elongata, 

 Leptosphaeria doliolum and two other species not precisely determined, and according 



FIG. 118. Pleospora AUernariae, Gibelli. (Determination not certain 

 from the absence of perithecia.) Young stage of development of pycnidia. 

 a commencement of the swelling and rapid transverse division of the 

 intercalary portion of a hypha, which is developing into a pycnidium and 

 has branches from itself and from an adjacent hypha attached to it. 

 * older stage of the development. The mature structure of these pycnidia 

 closely resembles that represented in Fig. 119, only the wall is formed of 

 several layers. Magn. 600 times. 



FIG. 119. Cicinnobolus Cesatii (De Bary, Beitr. Ill), para- 

 sitic on Erysiphe. A ripe pycnidium (seen from without) 

 open above on the left and discharging its spores J-, having de- 

 veloped in a gonidiophore of the Krysifhe which is attached 

 to the mycelial filament X X and bears four dead gonidia g on 

 its summit. B a small and nearly ripe pycnidium, formed on a 

 branch of a mycelial hypha m m of the Erysiphe, in which 

 the slender mycelial hyphae of the Cicinnobolus may be 

 seen. The figure shows the upper surface and the optical 

 longitudinal section of the transparent 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 discharged from the pycnidium and 

 a germinating spore. A magn. 380, B, C 600, D 300 times. 



to Zopf in 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. 



