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POPULAR SCIENCE REVIEW. 
During the summer it is not uncommon to find the leaves 
of some grasses, of the hop, of roses, and many other plants, 
covered with a kind of white mould, which appears under the 
microscope as a multitude of small transparent colourless cel- 
lules, generally attached to each other in a moniliform or 
beaded manner. These moulds were long known under the 
generic name of Oidium , to which genus the vine disease was 
also referred. More minute investigation, and more careful 
examination proved that these moulds were not in themselves 
perfect plants, but merely conditions of other fungi of a higher 
order, little differing it is true in external appearance to the 
naked eye, but offering material differences in structure under 
the microscope. Upon the white mould-like threads, spherical 
bodies are produced in the autumn, containing little sacs or 
asci filled with spores ; and in this condition the plants are 
arranged under the genus Hrysiphe, whilst the species of 
Oidium which represented their imperfect condition, are ex- 
cluded from the system. Here, again, we have examples of 
di-morphism. 
In the Journal of the Microscopical Society, Mr. F. Currey 
has detailed several instances of di-morphism which have 
fallen within his experience. In one instance he has shown 
that a small simple spored fungus, termed Oryptosporium 
Neesii, Ca., is only a state or condition of a fungus with com- 
pound fruit, belonging to the Sphceria section of ascigerous 
fungi, called Vais a sujfusa , Fr. Both plants are exactly alike 
externally, but the perithecium, or flask -like receptacle con- 
taining the fructification, in one instance only holds naked 
spores, and in the other the spores are contained in little 
elongated vesicular bags or asci, which are packed within the 
perithecium. 
Whilst writing this, one of the most wonderful books in a 
book-producing age lies beside me ; it is the second volume of 
a work on fungi, by the brothers Tulasne ; and this, as well as 
its predecessor, is devoted to this very subject of a multiplicity 
of form in the fructification of these plants. Illustrated by 
the most exquisite of engravings which art has ever produced, 
it also unfolds many a page in the history of these organisms, 
for which mycologists were not altogether unprepared. In 
noticing this work, one of our most eminent authors on myco- 
logical subjects quotes as an example Dothidea ribis, Fr., 
one of our most common fungi, which occurs in the form of 
little black shields on dead twigs of currants and gooseberries. 
Here we have, he says, naked spores ( conidia ) growing on the 
external cells of the stroma ; we have naked spores of a 
second kind (stylospores) produced in distinct cysts ( pycnides ) ; 
we have minute bodies of a third kind ( spermatid ) produced 
