AUTONOMOUS MOVEMENTS 531 



Peculiar nutations are met with in the leaves of ferns and of other plants whose 

 leaves retain the power of apical growth for a long time (e. g. Drosophyllum ; com- 

 pare GOEBEL, Organographie, p. 508, Fig. 336). Such organs have their apical 

 regions coiled in a circinate manner. In ferns this circinate condition is hypo- 

 nastic and, as the leaf straightens itself, a less vigorous epinastic curvature sets 

 in, ultimately bringing about the expanded condition. Similarly, in the case of 

 the nutations of many seedlings, where more vigorous elongation takes place on 

 one side of the plumule, usually spoken of as the posterior side, a second 

 curvature occurs on the incurved apical region at the zone of maximum growth 

 which acts antagonistically to the original curvature. WIESNER (1878) speaks 

 of an ' undulating ' nutation in this case, and of a ' simple ' nutation when the 

 region of the plumule behind the hooked end is straightened at once (Linum). 



In addition to autonomous movements in one plane we have also autono- 

 mous movements in space, such as torsions and twinings. Examples of this 

 type of movement are met with in the peduncles of Vallisneria and of many 

 species of Cyclamen after fruiting, leaves of the garden variety of Juncus known 

 as Juncus spiralis, leaves of Typha and many other narrow-leaved Monoco- 

 tyledons, the labellum of Himantoglossum, the internodes of Chara, and finally 

 the senile coilings of tendrils previously mentioned. We must limit ourselves to 

 the mere enumeration of such instances for they have not as yet been studied 

 in detail. It is not improbable that it may be found necessary to remove many of 

 these examples from the category of autonomous to that of induced movements, 

 as has already been done in the case of the nodding flower-bud of Papaver and 

 the apex of the shoot of Ampelopsis ; such cases of ' nodding ' would certainly 

 have been regarded as autonomous from their likeness to the nutation of plumules 

 had it not been that VOCHTING (1882) and SCHOLTZ (1892) have shown that 

 they are geo tropic in their nature. 



Glancing back over what has been said, we recognize in autonomous move- 

 ments phenomena which, as yet, are very imperfectly understood both from 

 the physiological and from the biological point of view hence the brevity of our 

 treatment of them. 



Bibliography to Lecture XLI. 



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M m 2 



