510 Report on the Cultivation of Potatoes. 



clucecl such havoc to the potato-crop for so many years." This 

 fungus was observed in France as long ago as 1851, on barley 

 and rye as w^ell as on wheat. 



Nevertheless, although the sum of the circumstantial evidence 

 is remarkable, it must be admitted frankly that at present we 

 have no proof of the identity of any one of the three fungi 

 (the potato-fungus, the clover-fungus, and the straw-fungus) 

 with either of the others ; and thej following remark made by 

 Mr. Carruthers, in describing the straw-fungus, applies with 

 equal force to the clover-fungus : — " No observer has yet noticed 

 the fructification of this fungus, and as the classification of this 

 group of plants is entirely based on the organs of reproduction, 

 it is impossible to determine without them the genus, or even 

 the group, to which this mycelium belongs." Yet it is known 

 that this straw-fungus does not belong to any of those parasitic 

 fungi which attack our corn-crops, and the natural history of 

 which has been worked out. It should also be stated that Mr. 

 Seels has informed me that potatoes had never been grown on 

 the land which bore the wheat attacked by the straw-blight in 

 1871 ; although this fact is of very little consequence, because 

 the exceedingly minute spores of these microscopic fungi may 

 be carried by the wind very long distances. 



If, however, it be granted for a moment, so as to enable me to 

 state the argument, that the spores' of the potato-fungus may find 

 a home on clover and straw, and, under a combination of cir- 

 cumstances favourable to their development (such as excessive 

 moisture in the early summer), may even germinate there ; or if 

 it be that the potato-fungus has two stages of existence, one of 

 which it passes on the potato-plant, and the other on clover or 

 straw (like the wheat-rust, which has one phase of existence on 

 the berberry and the other on wheat) ; then, in either case, it will 

 be seen at once that the systems of cultivation of the potato 

 which are dominant in the United Kingdom appear almost 

 expressly designed to enable the potato-disease to produce the 

 maximum amount of injury to the crops. It would also justify 

 the prevailing opinion that farmyai'd manure encourages the 

 ravages of the potato-disease, especially when applied in spring, 

 because the spores of the fungus would be in the manure on the 

 straw which had been used for litter ; and the manure applied in 

 the spring would be more likely to contain those spores in a 

 healthy state than that which had been exposed to the action of 

 the elements during the winter. It would also account for the 

 fact that many potato-growers have an odd-sounding fancy for 

 stable manure when sawdust or tan has been used instead of 

 straw for litter. 



