CHAPTER VII. PHENOMENA OF VEGETATION. PARASITES. 



371 



by Peyritsch 1 in the case of the house-fly. The health of the insect attacked by 

 these epiphytes seems to be very little disturbed. 



The development of the Entomophthoreae which attack insects has also been 

 given above (page 158). We may add here that the body of the insect is occupied in 

 essentially the same way as by the species of Cordyceps which will be described 

 below. The Entomophthoreae, like the Laboulbenieae, are, as far as is known, strictly 

 obligate parasites, and go through the whole course of their development, with the 

 exception only of a brief stage of germination, in and on their host while it is either 

 still alive or recently killed by their vegetation. 



The life-history of the species of Cordyceps which attack insects is more 

 complicated. Cordyceps militaris, as examined in caterpillars, may be taken 



FIG. 165. Cordycepi militaris, Fr. A secondary spores from the asci germinating in water on a microscopic slide. 

 a a single spore with one of its germ-tubes erect and branched, its extremity and the branches having formed chains of 

 gonidia. # three secondary spores germinating ; the germ-tube of one of them has risen into the air and formed a chain of 

 gonidia on its apex. B extremities of hyphae which have penetrated through the chitinous skin of a caterpillar, have reached 

 its inner surface and are abjointing cylindrical gonidia. C cylindrical gonidia with sprouts, from the blood of a caterpillar 

 attacked by the Fungus ; one extremity of d is fixed in a blood-cell extremity of a filiform gonidiophore which has grown 

 out of the skin of a caterpillar of Sphinx Euphorbiae killed by the Fungus and converted into a sclerotium. Magn. about 



400 times. 



as an example 2 . The ascospores formed in the orange-coloured club-shaped 

 stromata are ejected as narrowly filiform or rod-shaped bodies divided by transverse 

 walls before they leave the ascus into a row of many shortly cylindrical secondary 

 spores, which are at least 160 in number. When placed in any fluid, they usually 

 separate from one another, swell slightly, become rounded in shape and then put out 

 germ-tubes (Fig. 165, 3); sometimes, but not always, the spores become partially 

 united together again by means of short connecting tubes before they germinate. 

 Germination takes place on the surface of the skin of a caterpillar if it is only slightly 

 moist. The germ-tubes penetrate at once, and at any part of the surface, into the 

 chitinous skin of the insect. Here they enlarge into somewhat stouter fungal hyphae, 

 which ramify and in the simplest case make their way by a sinuous course into the 

 deeper layers of the skin, at length reaching the inner surface and insinuating them- 

 selves between the bundles of muscles and lobes of fatty substance of the creature. 



1 As cited on page 273. 



2 Bot. Ztg. 1867, p. i, and 1869, p. 



B b 2 



