T 7 2 DISEASES OF TREES 



COLEOSPORIUM SENECIONIS 



The genus Coleosporium is distinguished from the preceding 

 one by the teleutospores being formed out of several super- 

 imposed cells, each of which produces a unicellular promycelium 

 with a single sporidium. 



According to the investigations of Wolf and Klebahn, three 

 species of this genus produce aecidia on the leaves of the pine. 

 These include not only C. Senecionis, which occurs on various 

 species of Senecio (according to Wolf), but also C. Euphrasies 

 and C. Tussilaginis (according to Klebahn). The aecidium forms 

 are known under the names of Peridermium Pini acicola or 

 Peridermium oblongisporium^ the pine-leaf-rust. 1 



In the months of April and May the aecidia may be observed 

 on the one- and two-year-old leaves chiefly of younger pines, 

 occasionally also of old trees. The sper- 

 mogonia are found scattered amongst the 

 reddish yellow vesicles (Fig. 102), which 

 are only a few millimetres in size. The 

 former become brown with age, and thus 

 look from the outside like small black 

 blotches. The mycelium develops in the 

 interior of the leaf, where it passes the 

 winter, and in the following year it may 

 FIG. 102. The secidia again produce aecidia without killing the 

 and spermogonia of leaf Seeing that the leaves which are 



Fender miuni Pint . .... 



acicola on the leaves infested by the aecidia do not die pre- 

 of a pme - maturely, or at least not to any great ex- 



tent, the injury done by this form of the 



fungus is insignificant. Discoloured spots are merely formed 

 upon the leaves. 



Several species of Cronartium produce aecidia and spermo- 

 gonia in the cortical tissues of pines. These have hitherto been 

 grouped under the name Peridermium Pini corticola* The 

 disease, which occurs both in young and old woods, is very 

 prejudicial to the health of the trees. How infection takes place 

 whether it must always be preceded by an abrasion of the 

 cortical tissue, such as is induced by insects, woodpeckers, hail- 

 1 R. Hartig, Wichtige Krankheften der Waldbiiume, 1874. 

 * [This disease occurs every year on pines in this country. ED.] 



