Naturally enough, our reader will be debating within himself how these spores, which we have seen, are shed in such profusion, can enter the tissues of the plants which 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 spores, or the ultimate sporidia produced after three or four generations. It is possible that the granular or fluid contents of the spores may be absorbed by the plant, and as a result of this absorption, become inoculated with the virus, which at length breaks out in fungoid growths. Much has been done to elucidate this mystery of inoculation, but much also remains a mystery still. There is no doubt that the inoculation takes place at an early age,[2] probably in the seeds of many plants; in others it may be conveyed with the moisture to the roots; but the spores themselves have certainly not yet been traced traversing the tissues of growing plants. Footnote 2: Dr. de Bary has lately shown that in many similar instances the seed-leaves are inoculated. It will be necessary to refer more particularly to his experiments hereafter.