274 ‘s, tructural ond: Plosiological Botany. bi 
fesaepares was also formerly regarded as a distinet genus 
under the name Uredo. 
In the Pyrenomycetes there are four kinds of reproduc- 
tive organs, which are, as a rule, produced at different times 
on the same mycelium or receptacle. These Fungi usually 
first produce conidia, then spermatia enclosed in spermo- 
gonia, then stylospores within pycnidia, and finally asco- 
spores in perithecia. Any of these members of the series 
may, however, be wanting, except the perithecia. 
_ All Fungi—since they do not form chlorophyll—-require 
for their nourishment the previous formation of an organic 
substance ; they do not possess the capacity of assimilating 
food-materials, ze of transforming them into substances 
which will directly support their life. Many are therefore 
Saprophytes, growing on dead organic substances in a state 
of decomposition ; others are Parasites, growing on lying 
animals or plants. Many Fungi are Audophytes, living in 
other organisms ; only a few Zpzphytes, living upon them. 
Many Fungi go through their whole cycle of develop- 
ment on the same substratum ; in others the alternation of — 
generations already described is connected with a change of 
the ‘h st’ on or in which they live. Thus, the resting-spores 
of Puccinia hibernate on the haulms of grasses ; while the 
germinating filaments developed by the sporidia which are 
produced from them in the spring never germinate on grass, 
but penetrate into the epidermal cells of the leaves of the 
barberry, and rapidly develope there into the Fungus pre- 
viously known as cidtum Lerbertdis. ‘Vhe spores of this 
form, again, when they enter the stomata in the leaves of suit- 
able grasses, produce in them, and in them only, the my- 
celium of the Puccinia, which bears uredospores and resting- 
spores. 
The parasitic Fungi distur the normal development. of | 
their host, and cause contagious and not unfrequently fatal 
diseases. ‘Thus the mildew of young vines is due toa para-~ 
sitic Fungus, Ozdium albicans. The Fungus attaches itself 
