202 DIVISION II. COURSE OF DEVELOPMENT OF FUNGI. 



bends over and covers the apex of the archicarp, and it is presently delimited by a 

 transverse wall, forming a short nearly isodiametric cell, the 'antheridium,' which is 

 borne on the lower part of the branch as on its stalk. The archicarp now developes 

 into the sporocarp, being usually divided by a transverse wall into two cells, an upper 

 which becomes the solitary ascus and subsequently produces eight spores, and a lower 

 which as a stalk-cell bears the ascus. Tulasne has found two asci in a sporocarp 

 as a very rare and individual exception ; they were probably caused by the formation 

 of two transverse divisions in the archicarp-cell. The envelope-apparatus also 

 begins to be formed at the same time as the ascus. From 7-9 tubular outgrowths 

 appear close round the base of the archicarp on the hyphae which bear it and 

 the antheridial branch, and grow up round it and in close contact with it and in 

 close lateral contact with one another and with the antheridial branch, till they all 

 meet together above its apex. Each tube then divides by one or two transverse walls, 

 so that the incipient sporocarp is surrounded by an envelope formed of a single 

 layer of many cells. These cells then increase in size in the surface-direction, their 

 walls thicken by degrees and assume a dark brown'colour, and they thus form the 

 outer wall of the sporocarp. During this time they form no further divisions, but 

 those nearest the substratum send out rhizoid branches which spread over the 

 substratum ; and in some, but not all, species some of the cells at the apex of the 

 sporocarp form a number of hairs with delicate ramifications which are described 

 urider the name of appendiculae. Branches shoot out at an early period from the 

 inner surface of the cells of the outer wall, which insinuate themselves between it and 

 the growing archicarp, and ramify and develope into a dense parenchyma-like weft 

 without interstices formed of two or three or more layers of cells according to the 

 species ; this weft has been termed the inner wall of the sporocarp and compared 

 from its origin and arrangement with the paraphyses of more highly differentiated 

 sporocarps. With these formations the sporocarp in its envelope is complete in 

 all its parts, and they are followed by further considerable increase in size only, 

 which in the end chiefly affects the ascus and leads to a partial displacement of 

 the cells of the inner wall. The antheridial branch separates from the archicarp 

 when the branches begin to be formed from the inner wall ; it takes part with less 

 increase in size of its parts and less considerable change of shape in the formation 

 of the outer wall, between the other cells of which it remains laterally enclosed. 



The development of the sporocarp of the species of Erysiphe, under which 

 genus I include all the Erysipheae which do not belong to Podosphaera, agrees with 

 the above description except in certain points, the chief of which only will be 

 pointed out in this place; the reader is referred for further details to the account 

 given in another work 1 . The archicarp has the form of an elongated club- 

 shaped cell, curved spirally round a hooked antheridial branch. The two organs 

 are surrounded and enclosed by the tubes of the envelope, which give rise, as in 

 Podosphaera, to the outer wall of the sporocarp and to the inner wall which is 

 much more largely developed in these species. The antheridial branch enclosed in 

 the inner wall soon disappears from observation. The archicarp on the other 

 hand, lying in the basal portion of the sporocarp, grows into a curved tube and 



Beitr. z. Morph. u. Phys. d. Pilze, III. 



