24 
POPULAR SCIENCE REVIEW. 
cluster of plants of Tragopogon. Nor is this all, for our 
number represents only the actual protospores which are con- 
tained within the peridia ; each of these on germination may 
produce not only one but many vegetative spores, which are 
exceedingly minute, and, individually, may be regarded as 
embryos of a fresh crop of cluster-cups. And this is not the 
only enemy of the kind which this unfortunate plant is subject 
to, for another fungus equally prolific often takes possession of 
the interior of the involucre wherein the young florets are hid, 
and converts the whole into a mass of purplish black spores 
even more minute than those of the JEJcidium , and both these 
parasites will be occasionally found flourishing on the same 
plant at the same time (plate III. fig. 11). 
Naturally enough, our reader will be debating within himself 
how these spores, which we have seen are shed in such pro- 
fusion, can enter the tissues of the plants which give subse- 
quent 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 recom- 
mended 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 spon- 
gioles 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 dis- 
charged 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 
spores 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, probably in the seeds of many plants ; in others it may be 
