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and in bursting tlirougb the epidermis of vegetables. Hysterium
either does not discharge its pulp at all, or very obscurely, and
grows upon the bark of trees, but altogether destitute of crust
like Opegrapha. The above being the sole difference, and as the
plants resemble each other most closely in all the more important
points, I do not think it necessary to keep them separate,
as it would only tend to confuse the student. Having drawn
and dissected almost the whole of the species in both genera,
I am enabled to decide, from actual investigation ; and
it may be observed, that, in several species of Hypoderma,
particularly H . pinastri, Graminum, and Juniperi ( G r e v . )
the epidermis does not appear to be ruptured, but the receptacle
to be formed out of the substance of the vegetable itself
on which it grows ; or at least, so intimate a union to be formed
as to deceive the observer.
Fig. 1 . Hysterium Rubi. Fig. 2 . A receptacle. Fig. 3 . A receptacle open.
Fig. 4. Sporuliferous cells.~Fig. 2, 3, & 4, more or less magnified.
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