53P 



NA TURE 



[April lo, 1902 



Simple tactile papilla; occur in stigma lobes of Gold- 

 fussia anisophylht ; they are not highly sensitive, and a 

 pressure on them sufficient to bend the lobe is required, 

 but whether or no the deformation of the motile tissue 

 acts as an accessory stimulus is not easily decided. In 

 his section on irritable styles and stigmas, Ilaberlandt 

 describes the curious movements of the style of Arctotis 

 (Composita:), which was discovered by D. Miiller in 1853, 

 but has, until recently, received too little attention. Like 

 the filaments of Helianthemum, it has no special sense 

 organs, and Haberlandt suspects that the reaction is 

 called forth by the style being forcibly bent rather than 

 irritated by touch. 



In Darwin's " Fertilisation of Orchids " the mechanism 

 by which Catasetum shoots out its pollen-masses was for 

 the first time described. Ilaberlandt has now shown 

 that in C. Darzvinia/nan and iitacrocarpum the 

 " antenns " which receive the stimulus, and transmit an 

 influence to the rostellum, are provided with sense organs. 

 His drawings (especially Taf. iii. Fig. 7) fully confirm his 

 remark that the tactile papillic bear a striking resem- 

 blance to those on the filaments of Opuntia and Portulaca. 

 In an undetermined species of Catasetum a most re- 

 markable divergence from the type occurs. Tactile papilla^ 

 are wanting, and the antenna is converted, by the develop- 

 ment of mechanical tissues, into a vibrissa or lever ; it is 

 capable of bending near the base, and obviously functions 

 like filaments in Dionjea,' where the movement of the 

 stiff apical part deforms the percipient joint or hinge 

 near the base. 



Allied to the tactile papilhc are the FUhl-tiipfeln or 

 tactile pits discovered by Pfeffer in certain tendrils, inas- 

 much as by their means the protoplasmic prolongations 

 which fill the pits are brought close to the free surface, 

 and in such a position that they are liable to deformation 

 by contact. Haberlandt describes these structures in 

 detail in a variety of genera, and gives drawings of 

 several, including the cases where a relatively large 

 crystal is included in the pit, an arrangement which must 

 have the effect of a stone in a man's shoe in increasing 

 the sensitiveness to contact. -' 



For the interesting account of the minute tactile pits 

 in the tentacles of Drosera, the reader is referred to the 

 original. The remaining sense organs described by 

 Haberlandt may be placed together, although by the 

 author they are subdivided into tactile hairs, tactile 

 bristles, stimulators, &c. Their essential character has al- 

 ready been referred to in describing an unnamed species of 

 Catasetum ; it is the occurrence of a stift' terminal part the 

 movement of which deforms either the base or the tissues 

 from which it springs. A simple e.\ample occurs on the 

 contractile stamens of Ceniaurva niontami ; here the 

 sense organs consist each of a simple, strongly built hair, 

 the movement of which acts on the thin- walled basal 

 joint. Other organs of the same essential type have been 

 described ■■ in Aldrovanda, but here the sensitive joint is 

 not at the base, but in the middle of the hair. 



One of the most interesting points m the book is the 

 discovery of similar organs in Mimosa and Biophytum. 



1 Haberl.-iniit, " PhysioloKisih.; l'll.in^<:n.inalomi<:," Edit, h., j.. jSi. 

 •-' Ste also Haberlandt, " Physiologische Pnanzenanatomie, Edit, ii,, 

 i8q5, p. ,76. 

 ^ Haberlandt, " Physiologischc Pflan/enanatomic," Edit, ii., 1S96, p. 480. 



NO. 1693, VOL. 65] 



The sensitive lower surface of the pulvinus of Mimosa 

 ptidica bears a number of obliquely lying bristles, and 

 Haberlandt finds that the familiar reaction follows a touch 

 applied to one of these. To convince himself of the fact 

 the observer must, it seems, select a plant not in the 

 highest condition of irritability ; with a slightly sluggish 

 plant it is easy to convince oneself that the bristles are 

 the most sensitive part of the surface. The bristles are 

 of several types, of which the most interesting is 

 described as the "cork-squeezer" pattern. 



In the angle between the bristle and the surface of 

 the pulvinus is a projecting mass of cells, which will 

 necessarily be squeezed when pressure is applied to the 

 end of the bristle. The same mechanical contrivance is 

 found among the 0,\alid;i.' on the leaves of Biophytum, 

 the lever being in this case a stiff hair instead of a 

 bristle. The author points out (p. So) that the discovery 

 of these organs throws light on the question of the 

 biological meaning of the irritability of Mimosa. Their 

 existence does not seem compatible with Sachs' view- 

 that the response to contact is useful as a protection 

 against sudden violent hail- or rain-storms. On the 

 other hand, it lends support to Pfeffer's theory that the 

 movement of the leaf stalks serves to warn off small 

 creeping insects, &c. In Java and Singapore, where 

 Mimosa pudica is an introduced weed, Haberlandt has 

 seen the leaves react to visitors of this type. 



The book concludes with a short section on the com- 

 parison of the tactile organs of plants with those of 

 animals, in which the interesting point is brought out 

 that in insects the lever-like or hinged hairs bear a dis- 

 tinct resemblance to corresponding structures described 

 by the author in plants. 



Fr.\xci,'^ D.xrwin. 



A NEW TREATISE ON THE CALCULUS. 



An Elementary Treatise on the Calculus, luith Illus- 

 trations from Geometry, Mec/ianics and P/iysics. By 

 George A. Gibson, M.A., F.R.S.E., Professor of 

 Mathematics in the Glasgow and West of Scotland 

 Technical College. Pp. xix + 459. (London: Mac- 

 millan and Co., Ltd., igoi.) Price ys. bd. 



AMONG several notable characteristics possessed by 

 this work, the most prominent appears to be the 

 severity of its logic. In one important respect it differs 

 also from the usual English mathematical treatise— it 

 seems to speak to the student, warning him against too 

 probable error and giving him advice. This is a feature 

 which should be encouraged. The aim of the writer of 

 a text-book should be to educate his reader, frankly 

 recognising the imperfections of human nature, and not 

 merely to set forth a work of unassailable art full of 

 unimpeachable truths. 



While applied mathematics is the great field for the 

 e.xercise of such a method of treatment- -since erroneous 

 views on the part of students are at once more probable 

 and more numerous in this domain than in others— the 

 calculus is probably, in the field of pure mathematics, 

 the subject in which a student most needs the anticipation 

 of errors and difficulties : and the really philosophical 

 student will find in Prof Gibson's treatise a work which 



