224 



REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



tern take their origin, and, as its presence is 

 essential to the existence of the plant, it may 

 be considered to represent, functionally, the 

 stem of other vegetables. 



33. On the formation and development of 

 the germ in the Fungi, comparatively very few 

 researches have yet been made which are not 

 so deficient either in completeness or accuracy 

 as to be useless. This being the case, the best 

 mode of treating the subject seems to be to 

 select those isolated facts and observations 

 which are most to be depended upon, and 

 arrange them in such a manner as to serve as 

 a foundation for a general view of the subject. 

 The most simply organised Fungi known, are 

 undoubtedly those which belong to the genus 

 Torula. The well-known yeast-plant consists 

 of a single ovoid cell, whose membrane is per- 

 fectly simple, and encloses a slightly granular, 

 transparent fluid. It multiplies by the budding 

 out of its membrane at one extremity into a 

 projecting nipple, which soon becomes sepa- 

 rated from the original cell by a constriction. 

 As the newly formed germ enlarges, the con- 

 striction becomes more complete, and at last 

 separation takes place. After the Torulae, 

 which are the only examples we are acquainted 

 with of one-celled Fungi, come the innumerable 

 Hyphomycetes or thread Fungi,so called because 

 their reproductive, bears so small a proportion 

 to their vegetative system, that it is in many 

 cases altogether overlooked. The growing 

 terminations of the mycelium filaments them- 

 selves become individualised, so as to form 

 the germs, which separate from their parent 

 cells by constriction, as above described in 

 Torula. It is this acrogenous mode of spore 

 formation which Schleiden considers as the 

 character which distinguishes the true Fungi 

 from the Lichens*; the latter developing "many 

 spores simultaneously in the interior of a 

 larger parent cell or ascus." Among the higher 

 Hyphomycetes, however, the reproductive sys- 

 tem appears in a more distinct and developed 

 form. Thus, in Penicillium it consists of fila- 

 ments which spring perpendicularly from the 

 stroma, and are formed of elongated, club- 

 shaped cells, joined end to end. These stalk- 

 like filaments branch trichotomously in the 

 most beautiful manner. From their extremi- 

 ties there spring others, which are much more 

 slender, and consist of moniliform series of 

 minute ovoid segments, separated from each 

 other by constrictions, which are indistinct at 

 the base of the filament, but become more and 

 more complete towards its termination. At 

 this point the segments detach themselves, 

 and form the germs of the plant.-)- In other 

 genera, the perpendicular sporiferous filaments 

 are woven together into more complicated 

 structures, the varieties of which it does not 

 come within our present purpose to describe. 

 As respects their component elements and the 



* Schleiden places all the ascophorous Fungi 

 among the Lichens. V\ r e shall find, as we proceed, 

 that such an arrangement is altogether inadmissible. 

 (Schleiden, Principles of Scientific Botany, p. 157.) 



t Corda, Icones Fungorum, torn. i. p. 21. 



mode in which the spores are produced, they 

 do not differ from those noticed above. 



Fig. 14-1. 



Branching sporiferous filaments of Penicillium verti- 

 cillatum, about 150 diam. (Corda.) 



34. The basidiosporous Fungi are character- 

 ised by the presence of a distinct membrane 

 (hymenium), on the surface of which the 

 spores are developed by a mode which, 

 though it is still acrogenous, is considerably 

 more complicated. The hymenium always 

 consists of elongated pouch -like cells, ar- 

 ranged side by side, with their long axes 

 perpendicular to its surface, and in close 

 contact with each other. Some of these 

 cells are longer than their neighbours, and 

 from their free rounded ends, there emanate 

 processes (usually four in number) in the form 

 of pedicles. Upon the extremities of these 

 are borne oval cellules, which, though in their 



Fig. 142. 



A. basidium with its four basidospores, along with tu-o 

 other sterile basidia (Geaster rufescens),'3QQ diam. 



earliest condition they do not exceed their 

 pedicles in width, rapidly enlarge, and finally 

 separate by a kind of constriction. In some 

 basidiosporous Fungi, as in the Agarics, the 

 hymenium is external, and its surface exposed 

 to the atmosphere ; while in others, as in the 

 Gasteromycetes, it is internal, the spores 

 being thrown, when detached from their pedi- 

 cles, into one or more cavities enclosed in the 

 substance of the receptacle. Of the last- 

 mentioned division, we select a well-known 

 genus (Geaster), for the purpose of illustration. 



