FUNGI. 



247 



fruit is much larger, and was at one time considered a distinct genus of Fungi, and 

 described under the name of ^cidium ; but this term is now only used to designate a 

 particular form of fruit in the cycle of development of Puccinia. These secidium-fruits, 

 which arise from the same mycelium as the spermogonia^ lie at -^first beneath the 

 epidermis of the leaf, where they form a tuberous parenchymatous body {A), also 

 surrounded by an envelope of fine mycelial filaments. When mature the aecidium breaks 

 through the epidermis of the leaf and forms an open cup, the wall of which (the Peri- 

 dium, p) consists of a layer of hexagonal cells arranged in rows, and which are pro- 



FIG. 170.— Pucctnia graminis. A part of a vertical section of a leaf oi Berberis vulgaris with a young- aecidium-fruit ; 

 / section of leaf of Berberis with spermogonia sp and aecidium-fruits a; p their peridium ; at ;»; is the natural thickness of 

 the leaf which is enonnously thickened between x and y; lid. mass of teleutospores on a leaf of couch-grass ; e the ruptured 

 epidermis ; * the sub-epidermal fibres ; t teleutospores ; /// part of a mass of uredospores nr with one teleutospore t; sh 

 sub-hymenial hyphre {A and / from nature ; // and /// after De Bary). 



duced at the bottom of the cup from basidium-like mycelial ramifications. The bottom 

 of the cup is occupied by a hymenium, the hyphae of which have their apices exserted, 

 and are continually detaching new conidia-like spores, which, originally of a polyhedral 

 form in consequence of pressure from opposite sides, afterwards become rounded, and 

 separate from one another at the opening of the cup (/, a). The peridium itself has the 

 appearance of a peripheral layer of similar spores ; its cells however remain united, and, 

 like the spores, contain red granules. The aecidium-spores produced upon the leaves of 

 Berberis do not develope a mycelium unless their germination takes place upon the 

 surface of a leaf or stem of grass (as wheat or rye). The germinating filaments then 

 penetrate through the pores of the stomata, and the mycelium produced in the paren- 



