April 1, 1890.] 



KNOWLEDGE. 



113 



where it is grown chiefly for ornament. According to Mr. 

 Dyer, the Chinese account for its squareness in the follow- 

 ing way. They say that in the fourth century a.d. the 

 famous alchemist, Ko Hung, took his chopsticks (which 

 consist of slender rods of bamboo pared square) and thrust 

 them into the ground of the spiritual monastery near 

 Ningpo ; and then, by his thaumaturgical art, he caused 

 them to take root and appear as a new variety — the square 

 bamboo. 



Similarly a shoot which grows horizontally is led by the 

 same stimulus of gravitation to rectify any departure from 

 a horizontal position. Gravitation, then, does not cause the 

 bending when a displaced shoot endeavours to regain its 

 normal direction, but serves merely as a guide. By its 

 means the plant is made aware (so to speak) that it has 

 been displaced, and takes measures accordingly. If the force 

 of gravity were absent, the shoot would go on growing in 

 any position in which it might happen to be placed. This 



The growth of plants is one of the greatest mysteries of 

 nature, and nothing is more mysterious in their growth 

 than their limited but very definite power of movement. 

 How is it that some plants grow vertically upwards, like 

 the normal bamboo, others climb and twist, others creep, 

 and others grow in zigzag shapes ? How is it that some 

 turn towards the light, some away from the light, while 

 others place themselves at right angles to it "? And how is 

 it that if you peg down the young stem of a vertically 

 growmg plant it will bend upwards beyond the peg '? '■' No 

 doubt the proximate cause is natural selection ; they do 

 these things because they have found them advantageous. 

 ]5ut this does not tell us by what mechanism a plant is 

 enabled to keep on growing in the particular direction 

 wliicli it finds advantageous. We know that when a plant 

 bends in a given direction, the cells on the convex side of 

 the bend are more " turgescent," that is, more distended 

 with sap, than those on the concave side, and that the in- 

 creased turgescence of the former is followed by increased 

 rapidity of growth ; but what causes the distribution of 

 turgescence in the cells has not been clearly made out. It 

 seems probable, however, that wlien a shoot is growing in 

 its proper and natural direction, the chief force which 

 guides it and enables it to maintain that direction is the 

 force of gravitation. To this force the growing portions of 

 a plant are extremely sensitive. Consider, for example, the 

 case of a vertically growing shoot. Whenever it is acci- 

 dentally bent the force of gravity must evidently act upon 

 the portion above the bend, tending to curve it still more, 

 and causing a strain in the material of the stem. The 

 plant in some mysterious way is aware of this strain, and 

 the cells of the lower side of the bent portion are stimu- 

 lated to increased turgescence as compared with those of the 

 upper side, so that the under side would grow faster; and, 

 as the plant would turn upwards in consequence, any devia- 

 tion fi-om the perpendiciilar would tend to correct itself. 



[* A moat remarkable substance called Tabasheer is occasionally 

 /ound within the joints of Hauiboo which have been stunted in their 

 growth. From time immemorial it has been used .as a drug, and 

 seems to have been introduced into Europe by Arab physicians, who 

 gave it its peculiar name. It has tho smallest refractive index of any 

 known solid, and seems to be a colloidal (that is, non-crystalline) form 

 of silica, containini; air so intimately mixed with tho silica that the 

 vesicles containing the air cannot be seen under the miscroscope. Sir 

 David Brewster was the lirst to discover tho peculiar physical proper- 

 lies of Tabasheer ; he found that its refractive index was less titan 

 tlint of ira/rr, varying from l-llll in some yellowish specimens of 

 Tabasheer from Vellore, to 1-182,") in some whitish Tabasheer from 

 Nagpore. It is never perfectly clear, but always has an opalescent 

 appearance, probably due to the scattering of light by small vesicles 

 of air. Jlr. Thiselton Dyer says that it is always found on the j!oor 

 ■of the joint, except when the Tabasheer-bearing joint leans over, when 

 it is always found on tlie lower wnll.^A. C. Hanyard.] 



Leaf of Bamboo 



' may be proved liy causing a growing seed to revolve slowly 

 round a horizontal axis, so that at every revolution the 

 force of gravity may act upon it equally in all directions. 

 When a shoot is grown in these conditions, it is foimd that 

 its power of correcting deviations from any particular hne 

 of growth is lost. Similar reasoning applies to the action 

 of lightjon plants, but, as above stated, we do not know why 

 it is that plants respond to the stimulus of light or gra\ity ; 

 we only know that as a matter of fact they do so. 



Notices of Boolis. 



A Manual of Pahcoiitoloi/i/ for the I .se of Stmlentx. By 

 Henry Alleyne Nicholson, M.D., D.Sc, F.R.S., &c., and 

 Richard Lydekker, B.A., F.Z.S., &c. (WUham Black- 

 wood & Sons, Edinburgh and London. 1889.) Palaeon- 

 tology, or the study of fossil animals and plants, is every 

 year attracting a greater number of devotees, and among 

 them are foimd not only the geologist, to whom some 

 knowledge of the organisms which he meets with in the 

 various strata is a matter of necessity, but also the biolo- 

 gist, who finds that many of the problems presented to 

 him in his study of living creatures are elucidated by the 

 investigation of extinct forms. There is still a third 

 class, who make Paheontology their special work, not that 

 they regard it as a science distinct from Biology, but 

 rather as one of its larger branches, demanding for its 

 cultivation all the scientific energy of a lifetime ; at the 

 same time they are well aware, or should be, that the key 

 by w'hich fossil mysteries are to be unlocked is a sound 

 knowledge of the structure of living forms. 



By all these students the third edition of Dr. H. A. 

 Nicholson's Manual of VahKinUiUiiiii, which has just been 

 issued, will be gladly welcomed. The fact that it has 

 been found necessary to enlarge the work from less than 

 1,000 pages to upwards of 1,600 pages, and at the same 

 time to use smaller type, is in itself an mdication of the 

 wide field which it covers. The book is now practically a 

 new one, having been entirely re-written, and the portion 

 treating of the Vertebrata, which occupies the gi-eater 

 part of the second volume, is the work of Mr. R. Lydek- 

 ker, whose writings on fossil mammals and reptiles are as 

 well known us are those of Dr. H. A. Nicholson on many 

 groups of the Invertebrata. This division of labour, sup- 

 plemented, as the authors acknowledge, by assistance from 

 several specialists, greatly enhances the value of the work. 



The reader who is not well versed in geology should 

 read carefully the introductory chapters dealing with the 

 sedimentary rocks and the conditions under which animal 

 and vegetable remains have become embedded, and are 



