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mildewed, and to a very mischievous extent, though no berberry 
bush is near ; and when consequently the spores from which the 
mildew arose could not have derived their origin from the fungus 
of the berberry? To explain this, Mr. Berkeley thinks it pro- 
bable that, when the berberry is not at hand, the subsidiary rust 
spores, equally with the Puccinia itself, may have the property 
of reproducing the mildew ; the same mildew that attacks wheat 
being found on various grasses and reeds, such as grow in ditches 
and on the borders of fields—from which may arise a plentiful 
supply of spores—and the parasite, in this way, be propagated 
season after season without the Afcidioid form intervening. There 
are other cases analogous to this, Mr. Berkeley observes, in the 
vegetable kingdom ; .and so there are also in the animal kingdom ; 
in this last may be mentioned especially the case of a small gnat, 
the larve of which, according to recent discovery, give birth to 
other larve, and these again to others for several generations, 
without the mature winged state being previously attained.* 
I now pass on to the second disease in wheat spoken of by Mr. 
Stephens caused by insects. There are several different species 
of insects that attack corn ; but the insect here referred to, both 
by Mr. Stephens and Mr. Davis, is in all probability the wheat 
midge, whose history was so closely investigated by the late 
Professor Henslow, forming the subject of another communication 
by him to the “ Journal of the Royal Agricultural Society,” in 
1842. The wheat midge is a minute two-winged fly, that “ may 
be seen in myriads in the early part of June, between seven and 
nine o'clock in the evening, flying about the wheat for the purpose 
of depositing its eggs within the blossoms. From these eggs are 
hatched small yellow maggots, the larve or caterpillars a this 
fly ; and by these the mischief is occasioned.” 
It has not been exactly ascertained on what part of the flower 
* See two articles in Nature, vol. i., p. 516, and vol. ii., p. 318, from 
which much of what has been said above is taken. 
