34 British Uredinee and Ustilaginee. 
on the part of the fungus, which was combated by pro- 
tective efforts on the part of the parasite in conserving those 
spores which it does produce, but when full of vigour 
and fresh from the zcidiospore it is less careful of its 
spores. When it begins to feel the effect of exhaustion, 
and is unable to develop such energetic spores, it takes 
more care of those which are produced. 
The same is true of the quantity of uredospores them- 
selves. When the uredospores are produced directly from 
the zcidiospores they are much less copious than when they 
originate from other uredospores ; especially is this so when 
they have arisen from a long series of uredospores. The con- 
verse is observable in such species as Puccinia tragopogonis, 
where the teleutospore occurs often on the same leaf as the 
zcidiospore, and the uredospores are very few indeed. 
We have striking illustrations of the contrary condition 
with many hetercecious Uredines. In Australia, where the 
barberry is not an indigenous plant, and occurs only in 
gardens and shrubberies, the agriculturists complain not of 
mildew (P. graminis) as destroying their wheat crops, but 
of rust. Some years ago I received specimens of the 
affected wheat plants from New South Wales, Queensland, 
and South Australia, all of which showed a profuse de- 
velopment of uredospores in proportion to the teleutospores, 
quite out of all parallel to that which obtains in England.* 
Mr, C. J. Arthur informs me that this is equally true of 
those districts in the United States from which barberries are 
absent. The same occurs in this country with P. rudigo- 
vera, the uredospores of which are extremely abundant on 
our wheat crops in spring ; but the autumnal A®cidium is a 
very infrequent fungus, partly because the host-plants are 
none of them very abundant, and partly because, occurring 
* Plowright, ‘* Reproduction of Hetercecious Uredines,” Your. Linn. a 
Botany, vol. xxi. p. 368. 
