638 FUSCH 



sporid. These sporids will germinate only on the leaves of the bar- 

 berry, where they produce, first of all, a mass of interwoven hyphse 

 within the tissue, and then the peculiar reproductive bodies known 

 as cecidia (fig. 476). The 'secidium ' is a cup-shaped receptacle of a 

 bright red or yellow colour, which breaks through the epiderm of 

 the leaf, and discharges a large number of cecidiospores, which are 

 produced in rows or chains springing from basids at the base of the 

 receptacle. These are accompanied, often on the other surface of the 

 leaf, by spermogones, smaller spherical or flask-shaped receptacles, 

 which also eventually break through the epiderm, and are filled with 

 barren hyphae known as paraphyses. Among these are other shorter 

 hyphae or ' sterigmata,' from the extremities of which are abstricted 

 narrow ellipsoidal cells, the spermatia. The purpose of these is 

 unknown ; but they may be male elements which have lost their 

 function. The secidiospores will germinate only on the leaves and 

 stems of grasses, either producing the teleutospore-form directly, or 





^ V-w r**cr^4T^ CTPWW-* 'i 



FIG. 476. JEcidium tussilaginis : A, portion of the plant, magnified ; B, section 

 of one of the ' secidia ' with its spores. 



with its spores. 



giving rise to a third * uredo-form.' This consists of filiform basids, 

 each of which bears a round oval spore, the uredospore, which ger- 

 minates very rapidly, constantly reproducing the same form. The 

 same mycele which produces the uredo-form also gives rise subse- 

 quently to the teleutospore-form. The fungus usually hibernates 

 and remains in a state of rest in the teleutospore-form. 



Of the Peronosporeae (fig. 477) some species grow on the dead 

 bodies of animals and on dead plants, others are parasitic in the 

 living tissues of flowering plants, causing widespread diseases, such 

 as the potato -blight. On the mycele, consisting of a number of dis- 

 tinct septated hyphse, are produced the sexual organs, oogones and 

 antherids. Fertilisation is not effected by means of motile anthero- 

 zoids, as in other classes of fungi and of algae, but the antherid puts 

 out a cylindrical or conical tube-like process, the fertilisation-tube. 

 The antherids and oogones are each single enlarged cells produced in 

 close proximity to one another ; the fertilisation-tube is produced 

 from the part of the antherid which is in immediate contact with 



