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 






FıG.6. a and 5 Podosphi Castagnei, Lev. a epid I cells of Melampyrum sj 2 ;a branched ial hypha 
is creeping over the surface and has sent a haustorium into one of the cells (surface view). 5 vertical section through 
epidermal cells with mycelial hypha and a haustorium which has penetrated into a cell. ca spore (gonidium) of Erysiphe 
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 disk into an epid cell. a and 4 magn. 600, ¢ 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 pic, 5. Erysiphe (Oidium) Tuckert. My 
separable from it. At certain circumscribed spots, how- celial hypha with lobed attachment-disk on 
ever, they are firmly attached to the substratum, and 7g. un Tab. XN. "Mage rn man (Bol. 
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 
Cc 2 

