230 DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



from them. The cell-rows which bound the cavity project into it from the first with 

 radial convergence, and fresh ones are formed resembling these and between them. 

 The wall of the cavity is thus lined with slender converging rows of short cells, which 

 begin at once to form numerous pycnospores terminally and laterally on all their 

 cells by successive abjunction. These spores are elongate-cylindrical, very thin-walled, 

 2.8-4/1 in length and about half that breadth, and are surrounded by a hyaline 

 gelatinous or gum-like substance, perhaps the outer wall-layer. Imbedded in this 

 gelatinous envelope they are heaped up in large numbers in the interior of the 

 pycnidium. When their formation begins the outer wall-layer of the pycnidium, which 

 has hitherto been colourless, is thickened and becomes brown. At the same time 

 a narrow opening is formed in the wall usually at one, rarely at more than one, place 

 by the retreat of the cells from one another, and the orifice is usually surrounded 

 on the outside by a circle of projecting cells like short papillae. In this state 

 the pycnidium has reached its full development ; addition of water causes violent 

 swelling of the mucilage which envelopes the spores, so that they collect into a 

 gelatinous mass and are squeezed out of the narrow opening in countless numbers, 

 forming a tendril-like body or a round gelatinous drop according to the degree of 

 moisture ; they separate at once in water. 



All the vegetative cells of this Fungus and its allied forms show a tendency to 

 form thick brown membranes like those of the perithecia, pycnidia, and gonidia. 

 With these walls they can pass eventually into a long period of rest and return from 

 it under favourable conditions to vegetative activity and the formation of spores. 

 These resting mycelia, and detached single cells or portions of hyphae (gemmae), 

 may appear in numbers at the close of their culture and add to the variety of 

 forms. 



As regards the genetic relations between all these forms, we are only told of the 

 microgonidia, that they occur in company with other gonidial forms. Observers also 

 agree in saying that a mycelium is produced from the germinating ascospore, and can 

 first produce gonidia and then perithecia and pycnidia ; it behaves therefore in the 

 same manner as the rest of the gonidia-bearing plants described above as regards 

 the successive formation of organs of propagation, except in the matter of the pycnidia. 

 Gibelli and Griflfini saw a mycelium proceed also from the Sarcinula-gonidia, which 

 first produced similar gonidia and then perithecia ; sometimes in this case also 

 the mycelium which has grown from the two kinds of gonidia does not proceed 

 beyond the formation of gonidia. But the pycnospores, which swell strongly in a 

 nutrient fluid and even form transverse walls and then put out germ-tubes, produce 

 a mycelium from them which up to the present time has never borne anything but 

 pycnidia in cultures, even when these have been continued through a large number 

 of generations. It would appear probable that the mycelium could produce 

 perithecia when growing on its natural substratum, but this has not been proved. 

 While observers are agreed up to this point, the views of the Italian botanists differ 

 in other respects from those of Bauke. They are of opinion that two similar but always 

 distinct species are confounded together under the name of Pleospora herbarum, one 

 Pleospora Sarcinulae, which is constantly characterised by the presence of the Sarcinula- 

 gonidia and by larger ascospores, the other Pleospora Alternariae, which as constantly has 

 the Alternaria-form of gonidia. They found pycnidia only in P. Sarcinulae. On the 

 other hand according to Bauke a mycelium proceeds from the ascospores of the same 

 perithecium, which forms either pycnidia in company with Alternaria-gonidia or 

 perithecia with the gonidia of P. Sarcinula. The mycelium from each of the gonidial 

 forms always produces gonidia of the same kind as the one from which it proceeded. 

 Further observation must determine which of the two views is correct, but the 

 analogy of other Fungi makes that of the Italian writers the more probable. The 

 decision of this question is not important for our present purpose, because, as was 

 intimated above, in the one case we are dealing with one species with a great variety 



