202 Proceedings of Royal Society of Edinburgh. [sess. 
(Annals of Botany , vol. xi. p. 515) on the correlation of growing 
organs where the latent period is twenty-four hours ; for cases of 
wound fever in adult organs (Richards, Annals of Botany, x. 534, 
and xi. 29), for healing reactions in adult leaves (Blackman and 
Matthaei, Annals of Botany, vol. xv. p. 533), where the latent 
period is very prolonged ; and if fertilisation be regarded as of the 
nature of a traumatic as well as a chemico-vital stimulus, by 
those of Farmer and Williams. The latter show that a membrane 
forms around the egg ten minutes — phase of anabolic inertia — 
after entrance of the spermatozoid (Phil. Trans. Roy. Soc., 1898, 
p. 625). In other plants the anabolic phase is more prolonged. 
In contact-stimulation either of growing organs, where the re- 
sponse is a growth reaction, as in tendril climbers, or in adult 
organs, where it is a movement of variation depending to a certain 
extent on turgor changes, as in leaves of sensitive plants and of 
insectivorous plants, functional inertia finds expression in the 
phenomena of latent periods and of physiological insusceptibilities. 
Here the latent period — period of anabolic inertia— may vary from 
a few seconds, as in leaves of Dionsea, Mimosa and tendrils of 
Passiflora, to a few hours, as in the tendrils of Ampelidese. In 
the same genus, and to the same stimulus, the anabolic phase 
varies : thus in different species of Drosera, according to Darwin 
(Insectivorous Plants), it varies from ten seconds to twenty 
minutes. Again, physiological insusceptibility is seen in relation 
to the character of the stimulus. For tendrils, according to 
Pfeffer, the stimulus must be contact with a rough surface, i.e 
a series of simultaneous impacts at discrete points of the sensitive 
organ ; for Dionaea, two successive delicate impacts ; for Drosera, 
a prolonged series of successive impacts amounting to a pressure. 
Matters are complicated in these cases by the existence of sense 
organs, as in Mimosa, e.g., where, according to Ewart (Annals of 
Botany, vol. xi. p. 448), the leaf has special sense organs for light 
intensity and a different set for light direction. The list of 
examples can be indefinitely extended in the case of mature 
organs. Thus the researches of Ewart (Jour. Linn. Soc., vol. xxxi. 
p. 364) on assimilatory inhibition furnish a mine of illustrations 
of inertia in the two phases — (1) Katabolic and (2) Anabolic ; those 
of Arber on the assimilation of Halophytes (Annals of Botany, 
