12 THE PARASITIC FUNGI. 



of the Uxoasceae the bases of the asci penetrate deeply between 

 the walls of the epidermal cells, so forming an intermediate 

 stage leading to other Uxoasceae and endophytic fungi, with a 

 mycelium growing between, or in the cells of tissues which lie 

 deeper than the epidermis. 



The mycelium of Cycloconmm oleaginum grows in the epi- 

 dermal cell-membranes, branching dichotomously under the 

 cuticle and sending through it erect hyphal branches for pro- 

 duction of conidia.^ The germinating conidia of Sphaceloma 

 ampeiinum are said by De Bary to penetrate the cuticle, and 

 to produce a mycelium which spreads thereunder and breaks 

 out just before formation of conidia. Mycoidea parasitica, an 

 alga, lives under the cuticle of leaves of Thea and Camellia. 



We have next to consider fungi with a mycelium which 

 lives and multiplies in the intercellular spaces of living plants. 

 Like the Uxoasceae just mentioned, they push their way between 

 neighbouring cells and spread through the already existing 

 intercellular spaces. Numerous Uredineae behave in this way, 

 and towards the period of reproduction the mycelium is capable 

 of increasing so much that the cells of the host-tissues become 

 isolated and even displaced. The various species of Hysterium 

 have an intercellular mycelium, which kills those cells with 

 which it comes in contact. Certain forms, e.g. Caeoma pinitor- 

 quum and Periderniium pini (Fig. 247) possess a mycelium 

 which, while still intercellular, sends off here and there little 

 lateral branches into the host-cells. It is an easy step from 

 forms like these to forms whose mycelium is no longer strictly 

 intercellular, but derives nutriment by means of specialised 

 haustoria. 



Haustoria of the endophytic Parasites. 



A large number of endophytic parasites frequenting hosts which 

 do not immediately succumb to their attack, possess "haustoria" 

 or special organs for the acquisition of nutriment from the 

 cells of the host. The haustoria are lateral outgrowths of the 

 mycelium with a limited period of growth and a more or less 

 constant form. They are more varied in form, but otherwise 

 quite comparable with haustoria of the epiphytes, especially 

 with those of the Erysipheae. One of the simplest forms of 



' Figures in Funghi Parasitli, Cavara and Briosi. 



