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at ouce placed under two bell-glasses. Next day some pieces of grass with abund- 
ance of last year’s Puccinia graminis on them were laid upon two of the flower- 
pots, under one of the bell-glasses. The P. graminis had not at that time germin- 
ated; it had been for some time in my study, and, previously to being employed 
in this experiment, was soaked for about a week in pure water. The pots were 
watered and examined from time to time, and on July 28th, the wheat growing in 
the pots on which the grass stems were laid had true Uredo graminis upon it. 
The other wheat plants remained free from the fungus up to the end of August. 
The bell-glasses were thoroughly cleansed before being used, by being washed in- 
side and out, with a strong solution of cupric sulphate. The earth used was pur- 
posely taken from a few inches below the surface so as to be free from stray Uredo 
spores, and the flower-pots were new ones. The plants were uncovered for water- 
ing, three, or at the most, four times, and then only fora few seconds. The grass 
on which the P. graminis was, was cut into short pieces and laid flat upon the 
earth, so that as soon as the young wheat plants appeared above the surface, they 
came into direct contact with it. Some light will also be thrown upon this 
subject by the investigation of the other hetercecismal Puccinia. P. rubigo vera 
has this year been extremely abundant; hardly a specimen of Holchus lanatus 
exists in this neighbourhood without harbouring it. But the Zcidium which 
occurs on various Boraginacee I have never been able to find. This Puccinia 
recurs year after year on the same plants of Holchus with no boraginaceous plant 
in the vicinity. Again, only yesterday, I walked over some pasture land not very 
long reclaimed from the sea on which Puccinia coronata in both the Uredo and 
Teleutospore state occurred in the greatest profusion; and to my certain know- 
ledge there is no shrub of either Rhamnus frangula nor cathartica within four 
miles. All this points to but one conclusion, namely, that the hetercecismal 
Puccinie can propagate themselves without the intervention of their dicidia. 
The hetercecismal Puccini at present known are all found either upon grasses 
or earices. In this county they are seven in number, namely, P. graminis with its 
Gicidium on Barberry; P. rubigo vera with its dicidium on Boraginacee; P. 
coronata with its 4cidium on Rhamnus frangula and cathartica ; P. Molinie with 
its 4cidium on Orchis latifolia, &c. ; P. poarum with its Zcidium on Tussilago 
farfara ; P. caricis with its Acidium on Urtica dioica; P. sylvatica with its Aici- 
dium on Taraxacum officinale. As the Zcidium state is known to be the product 
of the promycelium-spores, one is led to consider whether there be anything in the 
structure of the grasses and carices inimical to the entrance of the germ-tubes of 
these spores. In the passage already quoted from De Bary, he speaks of the 
germ-tubes of the promycelium-spores not boring through the epidermis, and 
suggestively adds that ‘they remained as if they had been sown upon glass.’ 
Here, I believe, lies the explanation, these germ-tubes do not bore through the 
epidermis because they cannot. The amount of silica in Graminee is well known, 
and has been spoken of as ‘‘ Nature’s water-proof mantle;” it may with equal 
truth be said to be ‘‘ Nature’s spore-proof mantle.” The germ-tubes of the pro- 
mycelium spores, it will be remembered, are very diminutive structures compared 
to most of the Uredo and Atcidium-spores. They are not long enough to travel 
