144 



SCIENCE. 



BOOKS RECEIVED. 



The Power of Movement in Plants. By Charles 

 Darwin, LLD., F. R. S., assisted by Francis Dar- 

 win. D. Appleton & Co., Bond street, New York. 

 1881. 



The announcement of a new work from Dr. Darwin 

 brings joy to the heart of every naturalist, and the pres- 

 ent volume will be much cherished by botanists, because 

 it introduces a line of research which is comparatively 

 unworked and one which promises interesting results to 

 those who have time and patience to continue it. 



The object of Dr. Darwin in writing this book was to 

 describe and connect together several large classes 

 of movements common to almost all plants, which is 

 chiefly noticed in climbing plants, the tips of which 

 revolve, bending successively to all points of the 

 compass. This movement is called by Darwin circum- 

 nutation, and a plant is said to circumnutate. 



In the course of the present volume it is shown that all 

 growing parts of every plant are continually circumnu- 

 tating, though often on a small scale. Even the stems 

 of seedlings before they have broken through the ground, 

 as well as their buried radicles, circumnutate, as far as 

 the surrounding earth will permit. In this universally 

 present movement we have the groundwork or basis for 

 all the varied movements which are essential to the re- 

 quirements of plant life. 



Thus the great sweeps made by the stems of twining 

 plants, and by the tendrils of other climbers, result from 

 a mere increase in the amplitude of the ordinary move- 

 ment of circumnutation. The position which young 

 leaves and other organs ultimately assume is acquired by 

 the circumnutation movement being increased in one di- 

 rection. The leaves of various plants are said to sleep at 

 night, and it is shown that their blades then assume a 

 vertical position through modified circumnutation in 

 order to protect their upper surfaces from being chilled 

 through radiation. The movements of various organs to 

 or from the light are all modified forms of circumnuta- 

 tion, as are the equally prevalent movements of stems, 

 &c, toward the zenith, and of roots toward the centre 

 of the earth. The method of observation employed by 

 Darwin is thus explained : 



" Plants growing in pots were protected wholly from the 

 light, or had light admitted from above, or on one side as 

 the case might require, and were covered above by a large 

 horizontal sheet of glass, and with another vertical sheet on 

 one side. A glass filament, not thicker than a horsehair, and 

 from a quarter to three-quarters of an inch in length, was 

 affixed to the part to be ooserved by means of shellac dis- 

 solved in alcohol. The solution was allowed to evaporate 

 until it became sufficiently thick to set in two or three 

 seconds, and it never injured the tissues, or even the tips 

 of lender radicles. To the end of the glass filament an ex- 

 ceedingly minute bead of black sealing wax was cemented, 

 below or behind which a bit of card with a black dot was 

 fixed to a stick driven into the ground. The weight of the 

 filament was so slight that even small leaves were not per- 

 ceptibly pressed down. The bead and dot on the card 

 were viewed through the horizontal or vertical glass plate 

 (according to the position of the object), and when one ex- 

 actly covered the other, a dot was made on the glass plate 

 with a sharply-pointed stick dipped in thick Indian ink. 

 Other dots were made at short intervals of time, and these 

 were afterward joined by straight lines. The figures thus 

 traced were therefore angular, but if dots had been made 

 every one or two minutes, the lines would have been more 

 curvilinear, as occurred when radicles were allowed to 

 trace their own courses on smoked glass plates. To make 

 the dots accurately was the sole difficulty, and required 

 some practice. Nor could this be done perfectly when the 

 movement was much magnified, say 30 times and up- 

 ward, yet even in this case the general course may be 

 trusted." 



To make this clear we give a diagram of one of the 



most simple of Darwin's experiments, and the following 

 further explanation : 



" Brassica oleracea" (crucifera;.) — Radicle. A seed with 

 the radicle projecting .05 inch was fastened with shellac to 

 a little plate of zinc, so that the radicle stood up vertically ; 

 and a fine glass filament was then fixed near its base, that 

 is, close to the seed coats. The seed was surrounded with 

 little bits of wet sponge, and the movement of the bead at 

 the end of the filament was traced (see figure) during sixty 

 hours. In this time the radicle increased in length from 

 .05 to .11 inch. 



Brassica oleracea. circumnutation of radicle traced on horizontal 

 glass from 9 A. M., January «, to 9 P. M., February 2. Movement 

 of bead at end of filament magnified about forty times. 



We trust that those who would take up this subject 

 will consult this work, as the amount of detail there 

 given is most essential to a thorough comprehension of 

 this study, but in case any of our readers are unable to 

 do so, the explanation we have given may suffice. 



The chapters on the sleep of plants are most interesting 

 and instructive, and many discoveries relating to this 

 phenomenon are presented. 



There are also certain movements in plants which are 

 not due to circumnutation, such as when a leaf of the 

 Mimosa is touched it suddenly assumes the position as 

 when asleep, but this movement occurs from a different 

 cause to that which produces the sleep of plants. The 

 sleep movement of plants is due to modified circumnuta- 

 tion ; this would not happen from a touch. 



Space will not permit us to further describe this im- 

 portant branch of the subject, but we hope on a future 

 occasion to again refer to it, and offer some illustrations 

 of the most striking instances. But as Mr. Darwin ob- 

 serves, it is impossible not to be struck with the resem- 

 blance between the sleep movements of plants and many 

 of the actions performed unconsciously by the lower an- 

 imals. With plants an extraordinarily small stimulus 

 suffices ; and even with allied plants one may be highly 

 sensitive to the slightest continued pressure, and another 

 highly sensitive to a slight momentary touch. But the 

 most striking resemblance is the localization of their sen- 

 sitiveness and the transmission of an influence from the 

 excited part to another which consequently moves. . Yet 

 plants do not of course possess nerves or a central ner- 

 vous system ; and we may infer that with animals such 

 structures serve only for the more perfect transmission of 

 impressions, and for the more complete intercommunica- 

 tion of the several parts. 



Influence of the Ventilation of Must upon Alco- 

 holic Fermentation. — E. Rotondi considers that ventila- 

 tion mechanically promotes the decomposition of the sugar, 

 and acts also chemically, because the albumenoid bodies 

 are transformed into more diflusible matters, and because 

 oxygen by increasing the quantity of ferment indirectly 

 intensifies the fermentation. 



