302 BOTANY part ii 



together. The male nucleus jiasses into the oogonium by an opening which forms 

 in the cell walls (Fig. 318, 1-4). After fertilisation the oogonium is surrounded 

 by inv^esting filaments which sjiring from its stalk-cell or from that of the 

 antheridium (5), and the oogonium itself becomes converted into a multicellular 

 structure (6), In Sphae7-otheca the ascus containing eight spores arises from the 

 binucleate penultimate cell, while in Erysqihe and PhyUadinia this cell 

 exclusively or mainly produces ascogenous hyphae which in turn give rise to the 

 numerous asci. Before entering upon the formation of jierithecia, the Mildew 

 Fungi multiply by means of conidia abstricted in chains from special, erect hyphae, 

 from the tip downwards. These are distributed by the wind. The Mildew 

 Fungus of the Grape-vine occurs on the leaves and berries in America and has 

 appeared in Europe since 1845. This fungus, known as Oidiuvi Tuckcri, is the 

 conidial form of Unmiula necator {— U. spiralis), the small perithecia of which have 

 appendages spirally rolled at their free ends and are only rarely found (Fig. 319). 



Order 2. Plectascineae. 



The spherical perithecia have a closed peridium ; the asci are irregularly 

 ai'ranged witliin this. 



1. Aspergillaceae (™). Fructification small ; not subterranean. Here belong 

 two of the most common Mould Fungi, Aspergillus (Eurotium) herbariorum and 

 Penicillium crustaceum, Avhich live saprophytically on organic substances. Both 

 multiply extensively by means of conidia before they begin to form perithecia. 



In the case of Asjxrgillus hcrharioru7n, the conidia are abstricted in chains 

 from a number of sterigmata arranged radially on the spherical, swollen ends of 

 the conidiophores (Fig. 320). The conidiophores are closely crowded together, 

 and constitute a white mould, afterwards turning to a blue-green, frequently 

 found on damp vegetables, fruit, bread, etc. Some species of Aspergllhos are 

 pathogenic in man and other mammals ; thus A. fiimigalus, which lives in 

 fermenting heaps of hay at a temperature of 40° C, causes mycosis of the external 

 ear, the throat, and the lungs. 



In Pcnicilliuvi crustaceum, another widespread blue-green mould, the erect 

 conidiophores (Fig. 320) are verticillately branched. The spherical perithecia of 

 Aspergillus and Penicillium are produced later on the mycelium, but only rarely 

 occur in the latter genus. Their structure is more complicated tlian in the 

 Erysipheae. They develop from the sexual organs consisting of an antheridium 

 and a carpogonium provided with a trichogyne. The walls of tlie asci and the 

 surrounding pseudo-parenchyma disajipear in the ripe fructification which opens 

 irregularly by the rupture of the perij)heral layer. 



2. The Elaphomycetaceae have subterranean, truffle-like fructifications, the 

 peridium of which is sharply marked off from the powdery mass of spores derived 

 from the ascogenous hyphae. 



Elaphomyccs granulatus {Boletus cervinus), the yellowish-brown fructifications 

 of which are of the size of a walnut and have a bitter taste, occurs commonly in 

 woods in Eurojie. It is used in veteriuary medicine. 



3. The Terfeziaceae are distinguished from the preceding grouj) by the peridium 

 of the fructification not forming a sharply distinct layer. Species of Tei-fezia with 

 edible truliie-like fructifications occur in the Mediterranean region. 



Order 3. Pyrenomycetes 



The Pyrenomycetes comprise an exceedingly varied group of Fungi, some of 

 which are parasitic upon different portions of plants, and others are sajn'ophytic 



