476 BROOKLYN BOTANIC GARDEN MEMOIRS 
by the production of mechanical tissue would seem to be similar to 
that induced by other irritable phenomenona. In the formation of 
the spirals in tendrils there is considerable stress to be overcome and 
the constantly increasing weight of the various members of the plant, 
such as is associated with the development of foliage, fruit, etc., 
together with the effects of rain, swaying movements due to wind, is 
most admirably met by the production of mechanical tissues. These 
additional strains are taken care of by the same type of response as that 
induced by the stretching of plants with weights. Since the leaves of 
plants appear to be quite sensitive to contact it is readily conceivable 
how the more specialized haptotropistic responses to contact exempli- 
fied by tendrils could readily be evolved from simple contact irritability. 
There are, however, a large class including various types of reaction 
phenomena which do not fall under tropistic, nastic and taxic responses. 
These are the so-called wound reactions—traumatotaxis (reaction of 
cell nucleus). Traumatotropisms, illustrated by decapitated root, and 
positive galvanic currents on roots, are apparently direct responses to 
wound stimuli, as probably are the reactions first observed by Darwin 
resulting from the attachment of different substances to the root tip. 
In wound reactions, however, contact is involved to a greater or less 
extent, and more or less injury and abnormal conditions are associated 
with this class of phenomena. Most of the responses following wounds 
are local in their effect, although the organism as a whole may be 
affected even from relative insignificant mechanical injuries, as shown 
by the modification in the developments and functions of the several 
organs in mutilated plants. 
Representative types of this class are seen in the various accelerated 
growths produced by insects, fungi, bacteria, mechanical injuries, etc., 
and generally the reaction continues long after the primary or excitory 
cause has disappeared. Local accelerated growths, however, do 
not always follow as a result of the intrusion of pathogenic organism 
inasmuch as the nature of the response is determined to a large extent 
by the character of the tissue affected. For example, eel-worm 
infestation of roots may give rise to galls, whereas on stems such 
a response may not necessarily follow and even on roots these reactions 
differ. In many so-called wound reactions the degree of response is 
disproportionate to the stimulus responsible for the same. This is 
illustrated by feeble lightning discharges on trees, in which case the 
stimulus (lightning causing burning) lasts but a few thousandths of a 
second. The reaction, however, to such insignificant injury—often 
hardly perceptible and characterized by the destruction of a few 
cambium cells, may manifest itself for years in an accelerated growth 
of the annular rings adjacent to the injury. The flow of tissue in 
