176 



THE AMERICAN MONTHLY 



[August, 



tends towards the epidermis so as to enclose a mass of the newly-formed 

 spongy host tissue (fig. 3). In either case, however, as the basidia ex- 



FiG. 7. — Young ^cidium fruit of /Ecidium hepaticarum in vertical median section, showing 

 the manner in which the basidia arise : (a) epidermis ot host ; (b) a vegetative hypha ; (c) 

 an isolated hypodermal cell ; (d) a young basidium ; (e) a portion of the hyphal net-work in 

 solution. X 200. Original. 



tend, the tissues above them, fungus or host, are gradually dissolved 

 away, so that when mature only the fruit remains within the peridium. 

 Uredospores {Stylospores) . — The next spore formation in the gen- 

 eral order of development is that of uredo or summer spores, which 

 develop upon the glumaceous hosts after an infection by the aecidiospores. 

 The filaments collect in a circular, disk-like mat lying just beneath the 

 epidermis from which the basidia arise at right angles to the substratum. 

 The development of the spores is characteristic of conidia forms. The 

 basidia become filled with the graiuilar protoplasm coiumon to the 

 hypha3 and the apices become swollen so as to form a somewhat rounded 

 body, the young spore. For a time this is essentially hyaline, with the 

 exception of a small protoplasmic collection in the central region, which 

 now contains a quantity of yellow oleaginous matter, also to be found 

 in the neighboring h3'pha2. This central body gradually enlarges 

 until the whole cell finally becomes filled. By this time the spore 

 is being abstricted from the pedicel, and a new wall, the endospore, forms 



