liv PROCEEDINGS OF THE ROYAL HORTICULTURAL SOCIETY. 



whether he should pull the plants up and burn them. He also said it was 

 spreading rapidly, and he was afraid it might extend to other plants in 

 the same house as well as his Cucumbers. Dr. Cooke reported upon 

 them as follows : — " I have examined carefully the Melon leaves sent me. 

 They are certainly not affected with the new Melon disease, nor can I find 

 any trace of mycelium in the tissues, or the least evidence of fungus 

 attack. I am of opinion the mishap is due to some external cause, 

 like a sudden chill, and there is nothing to be found which is capable of 

 infecting other plants. In so far as the leaves sent to me are concerned, 

 I find no evidence of internal disease, and cannot recommend the destruc- 

 tion of the plants ; only their complete isolation may be prudent, so as to 

 prevent communication with other Melon or Cucumber frames. Close 

 attention may reveal the cause, but I cannot see why it should spread so 

 rapidly. As a precaution I should pick off and burn diseased leaves ; but, 

 if it is really a disease of internal origin, although it does not at all 

 resemble the bacteriosis of Cucurbits, the microscope fails to detect any 

 mycelium or spores in the tissues, which confirms me that it is not an 

 organic disease. I shall be interested to know if any discovery is made 

 from external surroundings, but as these are unknown to me I cannot 

 offer any suggestions." 



Potato Tuber Disease (Fusarium Solani, Mart.). — Dr. Cooke also contri- 

 buted the following : — " A circumstance has occurred within the past few 

 days which convinces me that we have a disease to contend with in stored 

 Potatos which has not hitherto been estimated at its true importance. 

 Not long since, some tubers were sent to the Committee, which, when cut, 

 showed black blotches, and at the time I was inclined to think they might 

 be caused by the ordinary Potato mildew running down the stems into 

 tho tubers ; but the microscope failed to give satisfaction, and the 

 inference remained in doubt. Since that time tubers have been sent, 

 which, when cut, exhibited the same blackened blotches. In one instance 

 this was supplemented by a great number of convex pinkish pustules on 

 the outside of the tubers, mixed with tufts of white mould. These pus- 

 tules were the external manifestations of a compact pink mould, which 

 has long been known to develop itself upon Potato tubers, but the general 

 impression has been that it was only a saprophyte, which flourished upon 

 spots already decayed. Mr. Worthington Smith intimated in 1884 that 

 Fusisporium Solani, as it was then called, was ' not peculiar to decaying 

 Potatos,' but was a veritable disease of stored Potatos, and of this there 

 can be no longer any doubt. The black internal blotches at length 

 become permeated by mycelium, which produces the characteristic conidia 

 wherever they reach the external air. The pustules are about the size of 

 a split hemp-seed, and sometimes larger, with a tendency to form rings, 

 or at least to grow in company, of a rather compact substance, of a pale 

 pinkish colour, often mixed with tufts of white floccose mould. The 

 conidia are profuse, of a spindle shape, curved, and narrowed towards each 

 end, divided transversely by three septa into four cells (40-60 by 7-8 /u). 

 When mature,they are apt to separate at the septa, and then the angular 

 ( ( lis become rounded, and either germinate at once, or undergo a period 

 of rest. It must be remembered that a very large number of conidia 

 are produced on each pustule, and that one secondary spore germinates 



