RELATION OF THE DISEASE TO FUNGI. 57 



(Plate in., fig 1.) I have seen the same or a very similar 

 fungus on glue and in other situations. 



(223.) Another species is also said to be found on the 

 decaying leaves, and likewise on the tubers. It has been 

 called the Botrytis infestans ; and this is the specific fun- 

 gus which Berkeley believes to cause the disease. There 

 cannot, however, be any question that the fungus is a con- 

 sequence, and not a cause of the malady. 



(224.) Berkeley says that this fungus* is to be found in 

 the first instance in the cells, before it bursts through. 

 The Botrytis is not always of the species described by 

 Berkeley, for Martius has figured a different one, to which 

 he assigns the cause of the malady, and has beautifully and 

 correctly figured the manner in which this kind of fungus 

 pushes forwards through the cuticle into the atmosphere. 



(225.) I am very uncertain about the species of fungus 

 figured by Berkeley. I have figured one something like 

 it, growing on the edge of a leaf, and another variety 

 which was growing upon an under-ground stem, and which 

 I take to be either the same or an allied species. (Plate 

 in., fig. 6; Plate iv., fig. 6.) 



(226.) A fungus is to be found frequently in the interior 

 of the tuber, amongst the grains of starch ; and in this case 

 the microscope shows nothing but starch and fungoid 

 fibre. The mass appears to the naked eye like a piece 

 of boiled potatoe. This is probably analogous to mush- 

 room spawn ; but to what species it may be assigned, I do 

 not with certainty know. (Plate vn., fig. 9.) 



(227.) A fourth species presents a reddish aspect, and 

 forms one great mass in the interior of the tuber. Ex- 

 amined with the microscope, the edges are one mass of 



3* 



