280 PUCCINIA GRAMINIS. PART n. 



leaf of a plant be examined, empty sporangia are gene- 

 rally found, and spores in different states of development. 

 The Puccinia Fabse, an entophyte on the common bean, 

 has but one spore in its cylindrical case, and is considered 

 identical with the Uromyces appendiculatus. Besides 

 male organs like those of the -ZEcidium, M. de Bary found 

 that the bean entophyte has four kinds of reproductive 

 organs, of which one alone reproduces the original form, 

 while the others present a well-marked alternation of 

 generations. The Puccinia forms a prothallus on which 

 conidia, or secondary spore dust cells, arise ; these se- 

 condary spores form a mycelium, on which an ^cidium 

 appears, whose orange-coloured fruit gives rise to a 

 Uredo, and the dust spores of the Uredo enter the leaves 

 of beans or peas, and grow into a Puccinia. All the 

 species of -ZEcidium are similar to one another, and M. 

 Tulasne is of opinion that they do not constitute a dis- 

 tinct genus, but that, like many of the Uredines, they 

 are merely a secondary form of 

 some other fungus, and inhabit 

 the same cavity, as in the case of 

 JEcidium cyparissiae and Uromyces 

 scutellatus, JEcidium. leucosper- 

 mum and Puccinia Anemones, and 

 others. 



The order Puccinisei comprises 

 epiphytes, as well as entophytes. 

 ^^ SK The mildew on wheat is caused by 

 f'< '^ the Puccinia Graminis (fig. 33), 

 M ^& $ . which attacks the stem of the plant, 

 f and appears on its exterior in a 

 Fig. 33. Puccinia Graminis. circular cluster of pear-shaped sep- 

 tate spore cases. These spore cases 



spring from a filamental mycelium, whose threads in- 

 terweave themselves among the soft tissue of the stem 

 of the wheat, and the fertile threads make their way 



