EXAMINATION OF ME. STEPHEN WILSOn's " SCLKROTIA." 75 



Mr. Greenwood Pirn (Gard. Cliron,, Jan. 17th, 1885) also 

 corroborated Mr. Stephen Wilson's results. Lastly, Prof. Trail, 

 in two Eeports to the {Scientific Committee of the Koyal Horti- 

 cultural Society (Gard. Chron., Jan. 17th and Feb. lith, 1885), de- 

 scribes a series of experhnents directly confirming Mr. Wilson's. 

 Prof. Trail succeeded in staining the residuum with magenta, 

 iodine, and other colouring matters, and stated that he had "no 

 doubt that the sclerotioids are masses of protoplasm coated with 

 calcium oxalate, probably in the form of minute raphides." He 

 failed to discover any signs of a cell-wall, but supposes that " the 

 outer surface" (of the residuum), "like a primordial utricle, must 

 serve as a wall." 



The oxalate of lime, so far accepted, was thus used to render 

 even more astonishing and unique what was sutticiently remarkable 

 before. The organism thus constructed by Prof. Trail would take 

 the place of Mr. Wilson's former mass of " hornified plasm," and, 

 at least in the opinion of the latter, be destined to " plasmodiate," 

 "myceliate," and eventually produce the potato disease. 



In repeating these experiments of Messrs. Wilson, Smith, Pirn, 

 and Trail with isolated " sclerotiets," there is no difHculty whatever 

 (beyond the ordinary one of manipulation) in discovering the sub- 

 stance left after treatment with nitric acid, and none whatever in 

 obtaining the same results from the various staining processes. 

 The difficulty lies in discovering any evidence of the truth of the 

 statement that the protoplasm is contained witJiin a coat of calcium 

 oxalate. The above observers took no pains to prove it to be so, 

 and trusted their case to the baldest assertion. Obviously it suited 

 Mr. Wilson's theory. The possibility of the protoplasm being 

 outside the oxalate of lime does not appear to have occurred to 

 them — obviously that would suit my interpretation of the matter, 

 and the theory would fall to the ground again. It is extremely 

 easy to prove that the "residuum" is outside. If, instead of 

 dissolving the calcium oxalate, the colouring matter (iodine 

 solution, for example) be at once applied to an isolated " sclerotiet," 

 the desired stain will be readily obtained. This will appear as a 

 delicate colouring, and not with the intensity that would result 

 were the whole mass to take up the stain. It is therefore apparent 

 that the stained substance is outside the oxalate of lime, and the 

 natural interpretation is that it is but the remains of the original 

 cell- contents of the potato leaf-cell in which the oxalate of lime 

 body was formed, adhering to the latter over the surface. 



Mr. Carruthers recently placed in my hands a letter from Dean 

 Buckland to Piobert Brown, enclosing leaves, &c., of a potato plant, 

 and asking, " Is the enclosed the same affection of the potato 

 leaves as that of the last two years?" The letter is dated July 

 19th, 1847, and the Dean, no doubt, referred to the potato disease. 

 There is no sign of disease on the leaves, which, however, contain 

 very abundantly Mr. Wilson's " sclerotiets." Mr. Wilson was thus 

 anticipated in his idea that these bodies are connected with the 

 potato disease. Mr. Carruthers then suggested to me that the 

 potato plants preserved in Sir Hans Sloane's Herbarmm should be 



