FUNGI. 



^55 



yeast-cell produces similar new cells by the protrusion of small projections at first re- 

 sembling warts, which soon attain the form and size of their mother-cell, and sooner or 

 later become detached from the narrow points of union. Usually they remain for a 

 time united, and thus form combinations of shoots which may perhaps be considered as 

 branched hyphae with short, roundish, easily detached segments. When the supply of 

 nourishment is less abundant, — for instance, when the yeast is grown on cut slices of 

 potato, turnip, Jerusalem artichoke, or carrot, the yeast-cells grow to a more considerable 

 size, their protoplasmic contents produce, by free-cell-formation, from i to 4 roundish 

 spores, which, when placed in a fermentable fluid, immediately form new yeast-cells 

 by branching and the detachment of the terminal cells. The fermentation of beer is 

 produced by Saccharomyces Cereuisicp, which occurs in two (cultivated) varieties, as yeast 

 of the lower fermentation, which take place between 4° and 10° C, and as the yeast 

 of the higher fermentation, which takes place at higher temperatures. The fermen- 

 tation of wine and cider is caused by S. ellipsaideus, conglomeratus , exiguus, Pastorianus, 

 and apiculatus, which are formed, together with other Fungi, on the surface of fruits, 

 and thus find their way into the expressed juiced 



(2) The Tuberaceee form, like most Gasteromycetes (with which they may easily be 

 confounded by the beginner), roundish, tuberous, bodies usually underground and often 

 surrounded by the copiously branched mycelium. Nothing is known of the first appear- 

 ance of the receptacle from the mycelium, and the development of the mycelium from 

 the spore has also not been followed ; no other kinds of spores than the ascospores 

 have been met with. The receptacle is always angiocarpous. It consists, when 

 mature, of an outer more or less thick pcridium, in which an inner and an outer 

 layer are usually distinguishable, the latter often provided with beautiful protuberances, 

 and of a tissue of hyphae enclosed within it, on branches of which the asci are 

 formed. A very simple structure is shown in Hydnobolitcs. The receptacle here consists 

 of a tissue formed of densely woven hyphae, in which are everywhere imbedded 

 numerous spore-mother-cells placed upon the branches of the hyphae. Only the super- 

 ficial layer of tissue, consisting of a fine down of sterile hypha^^, forms a kind of peri- 

 dium. In Elaphomyces, where the pcridium is firm and more highly developed, a mass 

 of slender hypha: with long cells springs from its inner side in every direction ; here 

 and there these are united more densely into larger discs and bundles projecting 

 inwards ; but there is no gleba divided into closed chambers. The cavities left in the 

 tissue formed of slender filaments are everywhere loosely filled by the hymenial tissue, 

 which consists of hyphaj 2 or 3 times thicker, formed of shorter cells, much bent and 

 woven into balls, and bearing the asci on the ends of their branches. When ripe the 

 whole hymenial tissue dissolves into jelly and disappears, while the mass of slender 

 filaments remains as a delicate Gapillitium between the loose dust consisting of spores. 

 In another group a sterile matrix may be distinguished in the interior with a number of 

 groups or nuclei of hymenial tissue imbedded in it, in which are again imbedded a number 

 of asci springing irregularly from the ends of the branches. In Balsamia there is a thick 

 pcridium, and the interior is divided into many narrow curved air-containing chambers by 

 means of thick plates of tissue which spring from the peridium, like the partition-walls 

 of the Hymenogastreee among the Gasteromycetes. To this is also related the genusTuber; 

 but the chambers clothed with the thick hymenium are very narrow, and much curved 



^ [Protomyces, P. macrosporm, infests the foliage of some species of Umbelliferoe. Its myce- 

 lium is coloured blue by Schultz's solution and produces spherical asci, which enclose great numbers 

 of minute spores. These spores conjugate in pairs, and the zygospore emits a germinatmg filament, 

 which penetrates the epidermis of the host, and developes a new mycelium producmg a new series 

 of asci. See De Bary, Beitriige zur Morph. der Pilze, i Heft.— Ed.] 



2 This and what follows is after De Bary, Morph. u. Physiologic der Pil: e, p. 91.— Compare 

 also Tulasne, Fungi Hypogcei. Paris 1857. 



