112 ANATOMY AND PHYSIOLOGY OF 



sometimes forms a globular mxcleiis imbedded in the substance of 

 the sporangium, as in the Pyrenomycctes, and sometimes appears 

 as a membrane lying free upon the outer surface of the sporan- 

 gium, as in Discomycetes and Hymenomycetes. In the higher 

 Fungi, the number of spores formed in a parent-cell is definite, 

 and we meet at once here that fixed numerical relation, which 

 remains the same in the formation of the spores of the Ciypto- 

 gamia and of the pollen-grains of the Phanerogamia throughout 

 the whole Vegetable Kingdom, according to which, usually four, 

 more rarely eight or sixteen, spores or pollen-grains are formed in 

 a parent-cell, while tlie number may also sink on the other side 

 to two or one. Among the Fungi, four spores are foimed in 

 the majority of cases (in the IIy7)ienomycetes), sometimes only 

 two or one in a cell ; in a few groups, as in the Tuheracem and 

 Discomycetes, the number rises to eight (L(^veille, "Ri ch. s, Vhy- 

 men, d Champign/' — Ann. cL sc. not. sec. sen viii. 321; Coida 

 "^Icones Fungorum"). 



In regard to the form of the parent-cells, two modifications 

 occur. In the Pyrenomycetes, Discomycetes, and Tuheracece, they 

 appear as longish utricles (asoi), in the cavity of which the spores 

 are developed by free cell-formation, after a previous production 

 of a nucleus, and then frequently (e. g , Peziza) each spore again 

 divides by a septum into two, sometimes even into more, cells. In 

 the Lycoperdaceoe and Hymenomycetes, on the contrary, four (in 

 rare cases only two, or one) protrusions of the wall of the parent- 

 cell are formed, each of wliich becomes the seat of the production 

 of a spore. These parent-cells are called hasidla. 



From the small size of the spores of most Fungi, it is not de- 

 cided whether the cell-membrane of the spore secretes a special 

 layer upon its outer surface in all cases (a kind of cuticle). In a 

 ffreat number this may be easily perceived ; like the outer coat of 

 loUeix-grams, it is frequently covered with reticularly connected 

 ridges, little spines, &c. In germination, the coat of the spore ex- 

 tends itself into a filament, which in the minute mildew-like Fungi 

 is capable of growing on into a perfect plant. Whether this pro- 

 duction of a new Fungus from a single spore occurs also in the 

 higher Fungi, or whether the filaments which grow forth fi-om a 

 number of spores germinating side by side, must become com- 

 bined into a common tissue, has yet to be decided by observation. 

 The latter is at all events a common process. (See Ehrenberg's 

 ^' De mycetogenesi, Nov. Act Nat Out." x. p. 1, 161.) 



In the Lichens the fructification of many Fungi (Pezizece and 

 Sphceriacece) is repeated most exactly. In the interior of the 

 thallus is formed a gelatinous nucleus of elongated cells, converg- 

 ing towards the central point, and embedded in an abundance of 

 intercellular substance. A portion of these cells become tubular 

 (asci or thecce) and produce the spores. In the naked-fruited 

 Lichens the thallus opens above the nucleus, and the latter spreads 



