FUNGI. oin 



the other forms of spores, their germinating filaments penetrating, as in the Perono- 

 spores, into and through the epidermis-cells (Fig. 171, C, sp and /), and thus reaching 

 the parenchyma. They there form a mycelium which produces the swelling of the leaf 

 constituting the first stage which we considered ; this mycelium again, generating sper- 

 mogonia and aecidium-fruits. (If within the cycle of this alternation of generations a 

 fertilisation or conjugation occurs, it must probably be looked for on the mycelium in 

 the barberry leaf, so that the aecidium-fruit would be the result of it.) 



III. The Basidiomycetes. Although the largest and most beautiful Fungi belong 

 to this order, yet their course of development is at present only very imperfectly 

 known. In contrast to the variety of form occasioned by the alternation of generations 

 in most other Fungi, and to the singular phenomena of the mycelium of the Ascomy- 

 cetes, it is very remarkable that similar processes have not yet been established in this 

 class. The origin from the mycelium of the usually large receptacles, and their further 

 development, are known in their more conspicuous features, as is also the mode of 

 germination of their basidiospores ; but the history of the mycelium before it forms the 

 receptacle is still unknown^ I must therefore content myself with a few morphological 

 explanations of the development of the latter in the most striking forms of the Hymeno- 

 mycetes and Gasteromycetes^. 



(i) Among the Hymenomycetes ^ the best known and most abundant species are 

 those commonly known as Mushrooms. The structure which is usually called the Fungus 

 is the receptacle which sprouts from a mycelium vegetating in the ground, or on wood or 

 some other substance. Usually, but not always, the cap (pileus) is stalked ; on its under- 

 surface the hymenial layer lies upon projections of the substance of the pileus of various 

 forms. In the genus Agaricus these projections consist of numerous lamellsR attached 

 vertically and running radially from the summit of the stalk to the margin of the pileus; 

 in Gyclomyccs the lamclhr form concentric circles ; in Polyporus and Dsedalea they ana- 

 stomose in a reticulate manner ; in Boletus they form closely crowded vertical tubes ; in 

 Fistulina they stand alone ; in Hydnum the lower side of the pileus is covered with soft 

 dependent spines like icicles, the surface of which bears the hymenium, &c. In many cases 

 the receptacle is naked ; in others the lower side of the pileus is covered with a mem- 

 brane which is afterwards ruptured (velum partiale), or the pileus and stalk are both 

 enveloped in such a membrane (velum universale) ; or finally, in a few species (Amanita) 

 both are found. This formation of a volva or veil is connected with the entire growth 

 of the whole receptacle ; the naked pilei are originally gymnocarpous, those covered by 

 a veil indicate the transition to the angiocarpous receptacles of the Gasteromycetes*. 

 Agaricus luiriecolor is to a certain extent an intermediate form between those with naked 

 ■pileus and those furnished with a universal veil. The receptacle in this species arises as 

 a slender cone on the mycelium (Fig. 172, I,a,b), and consists of parallel hyphae growing 

 at the apex (/, c) ; an outer layer of hyphae is present at an early stage surrounding the 

 whole body like a loose envelope ; afterwards the apical growth ceases, the branches 

 of the hyphae turn outwards beneath the apex (//, III) and thus form the pileus {IF), 

 the margin of which continues to grow centrifugally ; the lamellae are formed on its 

 under-surface, the distance of the mu-gin of the pileus from the stalk increasing, and 

 ■the loose peripheral layer of hyphx becomes stretched (/F, -z;), and forming a rudimentary 

 universal veil. An example of the formation of a stalked pileus with a partial veil is 

 afforded by the common mushroom {Agaricus campestrii). Fig. 173 shows at ^ a small 



^ [See however Oersted, Quart. Journ. Micr. Sc. 1868, p. 18. — Ed.] 



2 [On the TremeUini, see Tulasne, Ann. des Sci. Nat. 1872, vol. XV, p. 215 ; Journ. Linn. Soc. 

 vol. XIII, p. 31.— Ed.] 



3 On the doubtful forms of spores of some Hymenomycetes not produced on basidia, see De 

 Bary, Morph. u. Physiol, der Pilze, p. 190. On Exobasidinm Vaccimi, a very simple Hymenomycete, 

 parasitic on Vaccinium, see Woronin, Beiichte der naturf. Gesells. Freiburg, 1867, vol. IV, p. 397. 



* For further details on these processes see De Bary, Morph. u. Physiol, der Pilze, p. 16. 



