CLUSTEE-CUPS. 9 



seen_, are shed in sucli profusion^ can enter tlie 

 tissues of the plants wliicli give subsequent 

 evidence of infection ; in fact, how the yellow 

 dust with which the goatsbeard of to-day is 

 covered will inoculate the young plants of next 

 year. If one or two of these spores are sprinkled 

 upon the piece of the cuticle which we have 

 recommended to be removed from the leaf for 

 examination, it will be seen that they are very 

 much larger than the stomata or breathing-pores 

 which stud the cuticle : hence it is clear that they 

 cannot gain admittance there. There remains but 

 one other portal to the interior of the plant — 

 namely, the spongioles, or extremities of the roots. 

 Here another difficulty arises ; for the spores are 

 as large as the cells through which they have to 

 pass. This difficulty may be lessened when we 

 remember that what are termed the spores which 

 are discharged from the cups are not the true 

 spores, but bodies from which smaller seed-like 

 vesicles are produced ; yet, even then there will 

 be much need of an active imagination to invent 

 hypotheses to cover the innumerable difficulties 

 which would encounter their passage through the 

 vessels of the infected plants. The Rev. M. J. 

 Berkeley proved many years ago that the spores of 

 bunt, for example, may be caused to infect all the 

 plants the seeds of which had been placed in 

 contact with them ; but this affection did not 

 necessarily accrue from the absorption of the 



