18991 MICROSCOPICAL JOURNAL. 145 



.'Ecidium if sown on wlieat plants will give rise to the 

 wheat Puccinia, and the teleutospore of the latter will 

 produce the berberry ^]oidiura. This has been proved 

 by numerous experiments by Piowright, De Bary, and 

 others, not only in the case of the wheat Puccinia, but in 

 many other species. 



Various species of Puccinia may be met with on vio- 

 lets, grasses, plums, beans, willow-herb, primroses, this- 

 tles, ground ivy, box, periwinkle, and very many other 

 plants. iEcidium forms occur on colt's-foot, primrose 

 anemone, berberry, willow-herb, butter-cup, dandelion, 

 nettle, etc. 



The Smuts, UstilaginesB, are usually intensely black 

 and very generally occur in the floral organs, stamens, 

 ovary, seeds, etc , while the Uredineae are mostly brown 

 and yellow, and chiefly affect the leaves and stems of the 

 host plants. The best-known example — Smut of oats — 

 may be found in almost every cornfield in autumn, the 

 parasite converting the ear into a shrivelled mass of sooty 

 powder. The conidia or spores are exceedingly numer- 

 ous and very small. Another common, but easily over- 

 looked species is the Bunt of wheat. This is entirely 

 enclosed within the ear, and is not seen till the seed is 

 crushed which, instead of affording white flour, gives 

 only a blackish evil-smelling dust. Its conidia are much 

 larger than in the smut of oats, and delicately spinulose. 

 They give rise on germination to curious secondary spores. 

 Other smuts are met with on the goatsbeard, scilla, cari- 

 ces, scabious, silene, stems of buttercups, etc. 



Perisporiacei. — This is another group of true parasites 

 of which the Mildew of the vine and of the rose are the 

 best known, if not very typical examples, inasmuch as 

 their fructification is rarely seen. In their early stages 

 most of the species produce a white bloom on various 

 leaves, consisting of a well-developed mycelium, from 

 which arise jointed threads ; these readily break apart 



