GALLS. 265 
cushions, or excrescences, which gradually constrict the wounded 
place more and more, and, indeed, may finally entirely close it. 
Such enlargements of the tissue as are produced by outward 
influences are termed hypertrophies. hey occur not only in the 
form of excrescences, but also as variously shaped malformations, 
which should not be classed with the excrescences without 
further distinction. While, namely, the latter are to be regarded 
as a reaction produced in consequence of a single wound, the 
other anomalous formations, quite generally designated by the 
name of galls or cecidie, are of service to the insect or para- 
sitie plant which produces the wound. Hence there may be 
distinguished according to the respective organism, fungus- 
galls (mycocecidie)—for of all plants only the parasitic fungi 
produce such formations—and insect-galls (zoocecidix.) 
Whether, however, a plant or an insect is the cause of these 
formations, the symptoms are always the same. By a vigorous, 
and often greatly increased formation and division of cells, the 
affected part of the plant, which always consists of cells which 
are still capable of development, is very considerably enlarged, 
and manifold and often very strange malformations are pro- 
duced. An active conveyance of sap affords abundant nourish- 
ment, which is often so great that not only are the requirements 
fulfilled for the new formation of cellular tissue, but numerous 
surplus products (for instance, starch) also accumulate in the 
cells. Moreover, peculiar bodies (such as tannic matters) are 
also frequently formed in the cells of the gall, which are either 
wanting in the other tissues of the plant, or are contained in 
them in very much smaller amount. Upon such an activity of 
development, which is increased and qualitatively changed 
through irritation, essentially depends the formation of galls. 
In the fungus-galls, the hyphx of the fungus, nourished by 
the richly supplied -cells, penetrate the intumescence. In the 
case of the insect-galls, the interior, which is mostly hollow, 
serves as an abode for the insect; it there passes through its — 
entire course of development, from the egg to the perfect insect 
(Cynips galls of the Oak), and even through several generations. 
Since the galls seriously injure the plant only when they are 
