OOPHYTA. 139 
a thick integument, which is double—that is, fornied of an 
outer thicker coat (epispore) and an inner thinner one (en- 
dospore). After a considerable period of repose the rest- 
ing spores germinate by sending out a tube, as in Green 
Felt. 
289. The Fly-Fungus (Entomophthora musce), which in 
the autumn is so destructive to house-flies, is a member of 
a small order (Entomophthore) apparently related to the 
Water-moulds. It consists of small cells which grow in 
the moist tissues of the fly, and at last pierce the skin, pro- 
ducing minute terminal spores, which give the fly a pow- 
dery appearance. These spores (called, also, conidia) may 
be seen as a whitish halo surrounding the spot to which the 
fly, now dead, has attached itself. 
Resting spores have been observed 
in some species. They are round 
and thick-walled. 
290. The Mildews and White 
Rusts (Peronosporee) live parasiti- 
cally in the interior of higher plants. 
They are composed of long branch- 
ing tubes, whose cavities are con- 
tinuous throughout. They grow 
between the cells of their hosts,* 
and draw nourishment from them 
by means of little branches (haus- 
toria), which thrust themselves 
through the walls (Fig. 65). neg Marware iho 
291. The asexual spores (conidia) Hey ie Nace ote uo 
Magnified 300 times. 
are produced upon branches of the 
* In speaking of a parasite, the plant or animal upon which it feeds is called 
its host. 
