1 84 DISEASES OF TREES 



CJEOUA ABIETIS PECTINATE l 



This disease closely resembles the vesicular or columnar 

 rust, dEcidium columnare (Melampsora Goep- 

 pertiand], from which it is distinguished by 

 the presence of numerous spermogonia, and 

 by the absence of a peridium. It occurs 

 on the lower side of the leaves of the 

 silver fir, usually in the form of linear 

 sporogenous layers, which are situated on 

 both sides of the mid-rib (Fig. 116). It is 

 very abundant in the Bavarian Alps and 



FIG. 1 16. A fir-leaf in the woods near Passau, and is probably 

 f^al? C ' AbietiS to be met with wherever the silver fir is 



indigenous. 

 The damage which it causes takes the form of the diseased 



leaves falling off in the first year, but the injury is comparatively 



unimportant. 



HYMENOMYCETES (CAP-FUNGI*) 



Most of the Hymenomycetes are saprophytes, and develop their 

 mycelium in soil that is rich in humus, or in the interior of the 

 dead parts of plants, and especially in dead wood ; while the 

 sporophore, which is often of large proportions, appears on 

 the surface of the ground or on the outside of the plant. Only 

 relatively few of the Hymenomycetes are undoubtedly parasitic 

 in character, and, in the case of many, more exact investigation 

 must determine whether they are to be classed as parasites 

 or saprophytes. The peculiarity in the production of the spores 

 consists in their being simultaneously formed in fours at the 

 apex of .basidia, and that these basidia constitute a more or less 

 dense layer (hymenium), which may occupy a part or the whole 

 surface of the hymenophore. 



1 Reess, Die Rostpilzformen der deutschen Coniferen, p. 115. 



* [These include the " Mushrooms " and " Toadstools " in the wider sense: 

 we are still in want of a good English general term for them, and the trans- 

 lation of the German Hut-pilze does not really meet this need. ED.] 



