226 
PECULIARITIES OF PLANTS. 
a diminution of vitality of that portion of the leaf. The genus Botrytis belongs 
essentially to the division in which the plants are developed on dead animal or 
vegetable matter, on the putrid stems of herbaceous plants, for example. But one 
or two other species fix themselves on the half-dead spots of leaves and stems. The 
Botrytis parasitica, very abundant on Shepherd's Purse, (Capsula bursa pastoris,) 
occurs chiefly on parts already infected by the Uredo Candida, or late in the autumn, 
when the vegetative force is on the decline. Another species, Botrytis effusa, grows 
on spinach, and is said to prove very destructive, and on Chenopodium albidum; the 
appearance of the fungi is preceded by a yellow or brownish spot on the leaf, and 
the cellular tissue is nearly deprived of vitality before the fungus makes its 
appearance. We have then two sorts of fungi ; those which answer to the entozoa, 
which produce little inconvenience of the general functions of the plant, if not very 
numerous ; and those which inhabit the dead or dying portions of cellular tissue. 
"The mucorini, to which tribe the Botrytis belongs, is emphatically the inhabitant 
of putridity, and it is only in a few rare cases that species of this tribe are found in 
living plants, and even then the parts they infect have either partially or wholly 
lost their vitality." 
Without further referring to the Botrytis ox other fungous parasite, which had been 
seen upon some (not all) the leaves of infected potatoes, it is sufficient to say that 
Dr. Ayres is opposed to the idea, that to it is to be traced the origin of the 
malady. In fact, the conclusion appears inevitable, since the practical gardener 
must be familiar with numberless examples of fungi, fixing them upon flowers, and 
fruits, and leaves in the garden and in the flower-houses, whenever a puncture, an 
abrasion, a wound of any sort, provided it is followed by disease, or a decay of the 
surface or tissue. Analogy is therefore by no means wanting ; and we much 
question whether there be one well-attested evidence of any plant becoming a prey 
to a mould, mildew, or other manifest fungus, until it be previously debilitated. 
To dismiss the subject of mould and mildew, it suffices to observe that to the 
amateur, the gentleman, or indeed any one who may possess but one or two flower- 
houses, it becomes a consideration of moment whether mere beauty of flower and 
foliage, can ever be deemed a compensation for constitutional liability to such 
sources of deformity? A plant, for instance, so lovely as Thunbergia in most of its 
species and varieties, — though never perhaps infested with fungus, — is proverbially 
subject to acarus (plant spider) : for this reason it has been dismissed from some 
noble collections, and we now rarely see it. Two remarks apply to this subject. 
The first, we are aware, will be disputed by many who believe that a plant like 
Thunbergia will introduce its pest, and contaminate a whole house. Still we 
suggest that, with few exceptions, each plant has its peculiar insect ; a plant covered 
with acarus may stand almost close to a vine, without imparting one to its neigh- 
bour, which itself, in point of fact, is, under certain conditions, peculiarly liable to a 
black variety of acarus. 
Again, Thunbergia, if kept in that vigour of growth which it can attain, is rarely 
