23° TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



fusions between hyphae are occasionally seen (Fig. 3, c). 

 Hyphae are frequently found associated together, forming 

 strands of various sizes (Fig. 4). The hyphae are freely 

 branched, and entangled amongst them are a number of small 

 ovalconidia; examination shows that these have been budded 

 off from the tips of some of the hyphae. They are colourless 

 and thin-walled and measure about 8 x 4 yu (Fig. 3, d). Conidia 

 are developed in many species of Rosellinia, and, as already 

 mentioned, Hartig, in R. guercina, has described their pro- 

 duction on upright conidiophores which bear whorls of branches. 

 Owing to the condition of the material it is extremely difficult to 

 determine exactly how the conidia were borne, but branched 

 hyphae, resembling conidiophores, are present (Fig. 3, e), and 

 there is little doubt that the conidia were produced on these. 

 This is a point of importance in determining the relationship of 

 the present fungus, as in the allied species R. necatrix, R. aquila, 

 and R. radiciperda (described by Massee ^) the conidiophores 

 are of somewhat different types. 



On cutting sections it is found that hyphae are present in the 

 cortex of both root and stem, and extend inwards to the 

 cambium. These hyphae pierce the walls of the cells and bring 

 about their death and disorganisation. There is an interruption 

 of the periderm at various points on the stem, probably brought 

 about by early penetration by the fungus, and at these places 

 groups of hyphae are found entering the stem and spreading 

 into the cortex (Fig. 7). 



When the seedlings were received the mycelium showed no 

 trace of perithecia, and in order to encourage the development 

 of the fungus the plants were placed in a damp chamber. The 

 mycelium developed abundantly and after a few weeks perithecia 

 appeared, at first scattered singly among the hyphae (Fig. 5) 

 but soon developing in large numbers so that the greater part 

 of the mycelium is covered by them (Plate XIV. Fig. 6 and 

 Plate XV. Figs. 11 and 12). They are not present on the roots 

 but usually occur on the stem and lower leaves (Fig. 10). The 

 perithecia are at first greyish and embedded in the mycelium 

 (Fig. 5), but soon become black; when mature they are from 

 •7-1 mm. in diameter, and are provided with a small mouth- 

 opening at the apex of a papilla-like projection (Fig. 14). 



1 " Root Diseases caused by P'ungi," Kew Bulletin, 1896, p. i. 



