362 DIVISION III.-—MODE OF LIFE OF THE FUNGI. 
towards it, enters it and developes into a mycelium. If germination, which ‘occurs 
readily everywhere in a damp atmosphere, takes place on some other substance, the 
tubes grow irregularly in every direction and perish after a short increase in length. 
The entry through the stomata has been observed also in species of Entyloma? and 
Kuhn’s Polydesmus exitiosus®. Further instances will be found in pathological 
literature. 
Among endophytic parasites on animals I mention here the germ-tubes of the 
aerial gonidia of Cordyceps militaris (‘Isaria farinosa’), which I only saw enter the 
stigmata of caterpillars on which they had developed from the germinating spores? ; 
but this observation requires to be revised. 
The second case in which the germ-tubes or hyphae pierce through the firm 
membranes of the uninjured host is probably the more common. It is of course the 
form which occurs in all endophytes on unicellular organisms. Examples of it are 
seen in the case of parasites on higher plants in the germ-tubes from the sporidia of 
the Uredineae, excepting always Leptopuccinia Dianthi just mentioned, and in those 
of most of the Peronosporeae and Ustilagineae*; Polystigma rubrum ° together with 
many other Pyrenomycetes and Discomycetes, Claviceps also and the facultatively 
parasitic Sclerotinieae (see section CVIII) may be added to the list. It is to be 
particularly observed that the germ-tubes of these parasites on higher plants never 
penetrate into the host by a stoma. Even if the spore lies on or near a stoma, the 
germ-tube either pierces through a guard-cell, or crosses the cleft as it grows and 
pierces the wall of an adjacent cell. 
The germ-tubes of most of the insect-killing Cordyceps, Botrytis Bassii, and the 
Entomophthoreae belong to this class; their tubes pierce through the chitinous skin 
of the body of the host, and may begin to ramify in the substance of the thick 
chitinous skin of the larger caterpillars. 
Some parasites on plants show both modes of proceeding, for the same germ- 
tubes may penetrate through the stomata and through the membrane of epidermal 
cells; this is the case in Peronospora parasitica, Phytophthora infestans, and Exoba- 
sidium Vaccinii*®; species also of the mode of life of Sclerotinieae can enter the host 
by the stomata. 
-Finally, there are a certain number of parasites whose germ-tubes and hyphae 
penetrate into woody plants, not through uninjured surfaces, but where some wound 
has been received, and from thence make their way into open spaces, such as injured 
vessels (Nectria cinnabarina), or pierce through the cell-membranes. This is the case 
with most of the tree-destroying Hymenomycetes studied by Hartig, with Peziza Will- 
kommii and the species of Nectria which are parasites on trees. See section CVIII. 
From this series of phenomena which constitutes the general rule deviations occur, 
in two directions, but the deviations are connected with the rule by intermediate forms, 
One of these deviations is found chiefly in endophytes which vegetate intracellu- 

1 Bot. Ztg. 1874, pp, 93, 103. 
? Krankheiten d. Culturgewächse, p. 152. 
® Bot. Ztg. 1869, p. 590. 
+ Wolff, as cited on page 185.—Kiihn, i in en d. Naturf. Ges. Halle, 24 Jan. 1876. 
5 Fisch, in Bot. Ztg. 1882, p. 851. .--- 
6 Woronin, as cited on page 341. 
