British UrediitecB and Ustilaginecs. 



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 secidiospore 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 aecidiospores 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 Piiccinia tragopogonis, 

 where the teleutospore occurs often on the same leaf as the 

 iEcidiospore, and the uredospores are very few indeed. 

 We have striking illustrations of the contrary condition 

 with many heteroecious 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. grarninis) 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. rubigo- 

 vera, the uredospores of which are extremely abundant on 

 our wheat crops in spring ; but the autumnal i^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," Jonr. Liiui. See. 

 Botany, vol. xxi. p. 36S. 



