374 



UREDINEAE. 



Coleosporium. 



The teleutospores form a soft, reddish, waxy cushion, and 

 germinate in situ producing four-celled promycelia; in these 

 respects they exhibit great resemblance to Auricularia. Uredo- 

 spores are developed in chains. The aecidia, as yet known, 

 have a distinct peridium. 



Many species infect the needles of pine trees and produce 

 aecidia known by the generic name Peridermium ; other species 

 also known as Peridermium and living on bark are really 

 species of Cronartium. The species here mentioned with their 

 Peridermium-ioTm. on pine-needles, so much resemble one an- 

 other as to be almost indistinguishable, and 

 the question arises whether they are really 

 species, or only varieties due to difference 

 of substratum — habitat-races. 



Coleosporium senecionis (Pers.). (Britain.) 

 The sori are produced on leaves and stems of 

 various species of Senecio (without doubt on 

 S. vulgaris, S. sylvaticus, S. viscosus). The 

 uredospores are shed in June from yellow 

 spots. The teleutospores follow later on 

 dark-red patches, there they hibernate and 

 in spring produce a four-celled promycelium, 

 each cell of which gives off a sterigma with 

 one sporidium. The latter germinate on 

 needles of Pinua sylvestris. A mycelium is 

 formed in the intercellular spaces of the 

 needles, and, nourished by means of haustoria sunk into the 

 host-cell, perennates and produces crop after crop of aecidiospores. 

 Hyphae are produced in such numbers that the cells of the 

 needle-parenchyma are tightly pressed together, and those 

 adjacent to pycnidia and aecidia turn brown, secrete resin, and 

 die. The needles themselves, although filled with mycelium, 

 remain on the tree till the time of their normal fall. 



Pycnidia are developed by April or May under the cells of 

 the epidermis. They are little obtuse cone-shaped enclosures 

 appearing as brownish-yellow spots scattered over the inner 

 faces of the needles. On attaining maturity they rupture the 

 host-epidermis and give out their conidia. 



Fig. 20". — CoUospoHum 

 Aenecionis on a bifoliar 

 spur of Pinus Bijtvestris. 

 Peridia and scars of the 

 pycnidia are shown, (v. 

 Tubeuf del.) 



