OF AN ELM-TREE AT ST. ALBANS, 131 



and it was inferred that the mycelial hyphte of some fungus were 

 located in the alburnum and inner bark, living on the cambial 

 layers and epidermal cells, and by destroying them cutting off 

 the supply of sap to the parts above, the tree meanwhile being 

 outstripped in growth by its companion on the opposite side of 

 Upper Lattimore Road. This difference in gi'owth during three 

 years indicates the impoverishing power of the invading fungus, 

 and shows the rate at which elm -trees increase in height and 

 cii'ciimference. 



At last, in the early months of 1896, certain fungoid growths 

 appeared at the circumference of the wounds, for the stem had 

 been still further bitten by horses through the bark down to 

 the wood. They were of an irregular tuberculous or lobed 

 character, and yellowish in colour. As some of the outgrowths 

 were knocked oif, and I dreaded not having another oppoi'tunity, 

 I made a sketch of the lower part of the tree by lamplight on 

 the 3rd of February. B is a facsimile, the scar and cause of the 

 mischief being shown at a, the fungus at 5, and the recent abrasure 

 of bark at c, the last-mentioned being of no consequence, as this 

 part had been traversed by the mycelial hyphse of the parasite. 

 This by its presence had offered an inducement to the hungiy 

 animals, for it was not only on the side next Victoria Street, but 

 also at the back, that it was eaten off more or less, and nowhere 

 but overlying the fungal hyphae. A cluster of the fungus showing 

 the upper part of the pileus, natural size, is represented at E. 

 As there were no teeth, or very few, on the upper surface, it was 

 concluded to be Hydnum ochraceum, Pers., especially as the club-like 

 processes characteristic of Hydnum diversidetis, Fries., were wanting 

 or very indefinitely present on the margin. Eventually, however, 

 a fairly representative specimen, shown at F, natural size, was 

 secured, and from its regular spines, awl-shaped and three lines 

 long, proved to be H. diversidens. Probably both forms were 

 present, that is S. ochraceum and H. direrst'detis, for there is 

 frequently a strange consortism amongst fungi, rendering it 

 extremely difficult to pitch upon the right delinquent. In this 

 case, however, I consider that the enemy was M. diversidens, as 

 shown at F on the under-side. The pileus is thick and fleshy, 

 and probably edible, while that of if. ochraceum is thin and 

 coriaceous, and this species is certainly not the active agent in the 

 destruction of trees. The spores are shown at G, highly magnified. 

 They are borne in foui's on the basidia (c), and, being very minute, 

 are readily dispersed by wind, and those which happen to alight 

 on the wounded surface of a suitable host, gcnninate at once. At 

 H the spores are shown still more highly magnified. In the 

 wound of the tree the spore (/), by the stimulus of moisture 

 and the nutrition of the sap, develops a germ-tube from one 

 end {g), or both ends (A), and this geim-tube grows into the 

 crevice formed by the separation of the bark of the tree from 

 the wood, due to the wound. It then emits a ferment, breaks 

 down the living cell-walls, abstracts and appropriates their contents, 



