MR. BERKELEY ON THE POTATO MURRAIN. 25 



The peculiar habit of the species, as said above, contradicts 

 the notion of its appearance being the consequence of decay. I 

 have in vain tried to make the spores vegetate, as is so easily- 

 done with other species. The spores of Botrytis Bassiana, which 

 destroys the silkworms, and certainly is not the consequence, but 

 the cause of decay, because the disease is readily communicated 

 to the most healthy caterpillars even of other species, vegetate 

 readily* upon various substances. 1 do not assert that others 

 may not have better success ; but at present, in whatever way I 

 have tried them, I have not been able to get a single spore to 

 sprout, much less to propagate them upon foreign bodies. I do 

 not know of any single instance in which any of the nearly allied 

 species have been found in any other situation than growing 

 from the tissues of plants ; were this ever the case, they could 

 not have been overlooked, as their spores are so much larger 

 than those of other species of the genus. Botrytis cana is the 

 only species which approaches them in this respect, but it is dis- 

 tinguished at once by its cinereous flocci and its evident relation- 

 ship to B, vulgaris. The species are in fact as peculiar to the 

 living tissues of plants as are the several species of Puccinia and 

 Uredo, which could not exist, or at any rate be perfected, else- 

 where. The mycelium of the cereal fungi is known to exist from 

 the earliest period in corn, and is perfected only under favourable 

 circumstances ; and there is every reason to believe that the case 

 is the same with these essential parasites, which certainly do not 

 thrive on putrescent matter, but cause the decay of the matter on 

 ■which they thrive. The direct observations of Bauer, Corda, 

 and Leveille, prove merely what a thousand facts indicate, unless, 

 indeed, we have recourse to the notions entertained by many of 

 spontaneous or equivocal generation from languid or diseased 

 tissues ; for the question at last reduces itself to this, which is 

 indeed one involved in mystery, but which, as far as I can judge, 

 wherever the veil is partially lifted up, seems after all to point 

 to the same general laws by which the higher portions of the 

 creation are governed. 



To my own apprehension, then, it appears clear at least that the 

 cause of the premature decay and putrefaction of the haulm is to 

 be found in the parasitic fungus, in consequence of whose attacks 

 the tubers are unripe, and in a bad condition for preservation. f 

 Under these circumstances, if decay takes place, there cannot be 

 much matter of surprise ; and tliat, as in all cases of decay, 



* See Ann. des Sci. Nat., vol. 8, p. 257 ; vol. 9, p. 1, &c. Dr. Montagne 

 has made the spores sprout between two plates of glass. 



f Some persons were inclined to attribute the premature decay, as said 

 above, to frost ; but, as the Abbe Michot remarks, " Balsams, dahlias, and 

 other plants susceptible of cold did not suffer."— Rev. Bot., 1845, p 156. 



