CHAP. II. — DIFFERENTIATION OF THE THALLUS. — FILAMENTOUS MYCELIA. 19 



Careful investigations into the formation of the mycelia of distinct species of non- 

 parasitic Fungi are to be found especially in Brefeld's Untersuchungen iiber Schim- 

 melpilze. 



The formation of clamp-connections described above may be taken as an example 

 of a peculiarity which is characteristic of the larger groups. It occurs, as far as we at 

 present know, almost exclusively in the Basidiomycetes and chiefly in the Agaricineae ; 

 it is found in the Tuberaceae, but apparently in no other Ascomycetes. Its occurrence 

 in Peziza Sclerotiorum, as stated in my first edition, seems not to be confirmed in more 



FIG. 6. a and b Podosphaera Castagnei, LeV. a epidermal cells of Melampyritm sylvaticum ; a branched mycelial hypha 

 is creeping over the surface and has sent a haustorium into one of the cells (surface view), b vertical section through 

 epidermal cells with mycelial hypha and a haustorium which has penetrated into a cell, c a spore (gonidium) of Erysipke 

 Umbelliferarum putting forth germ-tubes on the epidermis of Anthriscus sylvestris. The smaller germ-tube on the right 

 is sending a haustorium from the lobed attachment-disk into an epidermal cell, a and b magn. 600, c 375 times. 



recent times. It is at present uncertain whether it is a feature of all the Basidiomycetes 

 or only of all the Agaricineae, and the more so as according to Brefeld it is frequent 

 in one species of the genus Coprinus, but comparatively rare in all the rest. 



A greater number of distinctly marked characters 

 have been observed in the mycelia of parasitic Fungi, 

 especially the Erysipheae, Peronosporeae, Uredineae, 

 and Ustilagineae than in other forms, and they have 

 been observed for a longer time. Such characters 

 occur chiefly in the formation of the haustoria of 

 many species and groups of species in those divisions ; 

 the following are examples of them. 



The mycelial filaments of the Erysipheae (Figs. 

 6, 7) are furnished with transverse walls, and their 

 numerous but distant branches spread themselves over 

 the epidermis of phanerogamous plants, being generally 

 closely applied to it, but at the same time easily 

 separable from it. At certain circumscribed spots, how- 

 ever, they are firmly attached to the substratum, and 

 in these spots they are provided with a haustorium 



which, springing as a branch from a cell of the mycelium in the form of a very 

 delicate tube, pierces the outer wall of the nearest cell of the epidermis and enters 

 its cavity ; there it enlarges into an ellipsoid or somewhat elongated persisting vesicle 

 filled with protoplasm, which in Erysiphe graminis is branched in a peculiar manner. The 



c 2 



FIG. 7. Erysiphe (Oidiiim) Tucteri. My- 

 celial hypha with lobed attachment-disk on 

 the surface of a grape. After v. Mohl (Bot. 

 Ztg. 1853, Tab. XI). Magn. 570 times. 



