MILDEW AND BRAND. 
183 
savansj or farm-labourers, that the mildew is very injurious to 
the corn crop. Different opinions may exist as to how the 
plants become inoculated, or how infection may be prevented 
or cured. Some have professed to believe that the spores, 
such as we have seen produced in clusters on wheat straw, 
enter by the stomata, or pores, of the growing plant, “ and 
at the bottom of the hollows to which they lead, they ger- 
minate and push their minute roots into the cellular texture.” 
Such an explanation, however plausible at first sight, fails on 
examination, from the fact that the spores are too large 
to find ingress by such minute openings. It is impro- 
bable that the spores enter the growing plant at all. The 
granular contents of the spores may effect an entrance either 
through the roots or by the stomata, or the globose bodies 
produced upon the germination of the spores, may be the 
primary cause of infection. We are not aware that this question 
has been satisfactorily determined. It is worthy of remem- 
brance by all persons interested in the growth of corn, that the 
mildew is most common upon plants growing on the site of an 
old dunghill, or on very rich soil. As the same Puccinia is 
also to be found on numerous grasses, no prudent farmer will 
permit these to luxuriate around the borders of his fields, lest 
they should serve to introduce or increase the pest he so much 
dreads. 
The germination of the spores of the corn mildew is a very 
interesting and instructive process, which may be observed 
with a very little trouble. If the spores be scraped from the 
sori of the preceding year (we are not sure that those of the 
current year will succeed) and kept for a short time in a damp 
atmosphere under a glass receiver, minute colourless threads 
will be seen to issue both from the upper and lower divisions 
of the spores. These will attain a length several times that of 
the spores from whence they spring. The extremities of these 
threads ultimately thicken, and two or three septae are formed 
across each, dividing it into cells, in which a little orange- 
coloured endochrome accumulates. From the walls of each 
of these cells, or joints, a small pedicel, or spicule, is produced 
outwards, the tip of which gradually swells until a spherical 
head is formed, into which the orange-coloured fluid passes 
from the extremities of the threads.* A quantity of such 
threads, bearing at their summits from one to four of these 
orange-coloured, spherical, secondary fruits, supply a beautiful 
as well as interesting object for the microscope. When matured, 
these globose bodies, which Tulasne has called sporidia , 
fall from the threads, and commence germinating on their own 
* Similar in all essential particulars to the germination of Aregina (fig. 15). 
