MR. BERKELEY ON THE POTATO MURRAIN. 17 



rection, and becoming confluent ; they at length extend beyond 

 the barrier of vascular tissue, and attack the central mass. The 

 tuber, meanwhile, assumes a disagreeable smell, decomposes more 

 or less rapidly, other fungi establish themselves on the surface, 

 or in the decaying mass, which emits a highly foetid odour re- 

 sembling that of decaying agarics, the union of the cells is 

 dissolved, animalcules or mites malce their appearance, till at 

 last the whole becomes a loathsome mass of putrescence. The 

 eyes* are usually the last part destroyed, from the disease being 

 peculiar to the cellular tissue, and not very readily spreading 

 beyond it : and, in consequence, extremely decayed tubers will, 

 •when planted, vegetate and produce healthy shoots, which sup- 

 port themselves as tlie decay of ihe mother plant proceeds by 

 their own roots.f Meanwhile, the traces of mycelium are some- 

 times more evident, though often extremely obscure : but the 

 walls of the cells, when divided, often take so tortuous a course, 

 assume so many forms, and are so confused by the brown 

 granules, that it is extremely difficult to distinguish any myce- 

 lium from them, and no appearance can implicitly be trusted, 

 except when the threads are seen to float freely on the edge of 

 the portion examined ; and even where this has been satisfactorily 

 ascertained in a portion of a slice taken immediately below one of 

 the tufts of mould, it is very difficult to perceive it on another. 

 Indeed, on examining the diseased spots on the smooth surface of a 

 divided potato which had given rise to an abundant harvest of 

 the Botrytis, though the mycelium was clear enougii at the edge 

 of a thin slice, it was almost impossible to trace it farther, from 

 tlie confusion caused by the various septa, either divided by the 

 lancet, or seen through the superincumbent tissue. I have seen 

 one case only in which the spots did not give rise in the first 

 instance to the peculiar mould ; but this was in a specimen 

 already highly diseased and partially putrescent. In an earlier 

 stage of the disease the Botrytis is uniformly produced, and 

 at the time of writing these notes (Nov. 22nd) I cannot find, 

 in my potatoes which have been kept dry, any other species of 

 mould except on portions injured by the fork, which exhibit 

 some of the commoner species, and on parts which have been 



* The eyes of the decayed tubers often show a remarkable tendency to 

 shoot. I believe this is the case principally in such specimens as have been 

 exposed to light. 



f It remains to be seen what will be the ultimate condition of these plants. 

 I do not apprehend that the decayed tuber beneath will injure the plants when 

 they are once established ; but the shoots if not produced rapidly sometimes 

 fail, partly, as it should seem, by immediate imbibition of diseased juices, 

 partly from the contiguity of diseased matter. See ' Gardener's Chron.,' 

 1845, p. 768, c, for some observations bearing on this subject. 



VOL. I. C 



