{Murros/Ktfii'r/t snlani. Cooke), proving tliiti this disease run 
also be perpetuated by hybernation mycelium present in the 
The above experiments, in addition to proving that the diseases 
indicated can be transmitted from one generation to another by 
means of mycelium present in the tubers, also demonstrate 
another point of much practical importance, namely, that the 
absence of <>brion-< disease in a crop does not necessarily prove 
the absence of such disease in a latent form. 
In the experiments described above, it was known at the 
commencement that the six half-tnbcrs were all diseased. The 
three plants grown in the hot. d house were 
prompt!} des licafed were 
detrimental to the growth of the potato but highly favourable to 
the rapid development of the fungus, which soon became 
dominant , el [esi oyed its host-plant. On the other hand, the 
three po;ah. plants in the cool house grew normally under the 
lower temperature, less atmospheric moisture and Letter light, a 
set of conditions very detrimental to fundus -rowth ; hence, 
although the parasite was present, it remained entirely in abey- 
ance, and the practical man would, without hesitation, have 
pronounced the plants free from disease. 
Every potato grower of experience can predict almost with 
certainty the moment when potato disease will appear: the 
»i:«*™> <-"»di on, , u-m. dam lull w. tth r, but insn il 
of the sudden outbreak hem- due to the rapid diffusion of spores, 
as has hitherto been believed.it i- far more probable that in the 
XXI.-NEW ORCHIDS. DECADE ! 
Masdevallia peruviana, Rolfe • affinis 1/ 
cm. longi, 1-2-fto 
tubum late cupu 
laterales latissin 
