NATURE 



[November 5, 1891 



usually from twenty to twenty-four inches long, and 

 occasionally as much as forty ; and it is capable of 

 growing even should it fall where it is wholly under 

 water in the early stage of its further development. 

 When the young plantlet is ready to separate from the 

 parent, the aperture made by the growing radicle is 

 sufificiently large to allow the inclosed or apical end 

 to slip out, leaving the empty fruit still attached to the 

 branch. And when this happens, there is a fully-formed 

 leaf-bud at the top, from which the stem is developed. 

 The primary root does not grow much after falling, but 

 stout secondary roots are thrown out from this axis, 

 successively, one above the other ; and as they assume 

 an arched form, and are produced in all directions, the 

 plant becomes very firmly fixed. The American Rhizo- 

 phora Mangle is very closely allied to the Asiatic and 

 African R. mucronaia ; but whereas there is only one 

 genus and one species of the order in the New World, 

 there are several in the Old. 



Singular to say, the only herbaceous plant of the 

 Asiatic YS\?i^\gxo\t.?,, Acanthus t'h'a/oh'us, is su^ ];.cn(:d by 

 similar stilt-roots. Most of the other trees and sLrubs of 

 the mangrove vegetation have horizontal roots, often of 

 enormous length and strength, and some of them produce 

 the so-called knee-roots in great abundance. These 

 roots grow out of the ground, at an angle of about 45^, 

 to a height of a foot or two, or perhaps more, and 

 return to the ground at about the same angle, forming an 

 anchor-like attachment. But their function is not merely 

 to hold the plant. They are abundantly furnished with 

 lenticels, through which the interchange of gases takes 

 place — at least, such is the opinion of several eminent 

 physiologists. Indeed, Karsten designates them breath- 

 ing roots. Schimper figures negative geotropic roots of 

 Avicennia tometitosa, which grow quite erect, from a 

 thicker horizontal root, to a height of about a foot, and are 

 either undivided or forked, and taper to a point. They 

 are thickly studded with lenticels, as are the stilt-roots of 

 Rhizophora. Another modification of root-production is 

 exhibited by some of the mangrove-trees. Like Rhizo- 

 phora, they produce aerial roots ; but, instead of their 

 remaining free, they eventually grow to the stem and 

 outwards, forming plate-like buttresses. 



Many other interesting facts might be exti-acted from 

 the papers cited ; but enough has been said to give an 

 idea of the nature and value of their contents. 



W. BOTTING Hems LEY. 



RICARDO'S "POLITICAL ECONOMY." 

 Principles of Political Economy and Taxation. By David 

 Ricardo. Edited, with Introductory Essay, Notes, and 

 Appendices, by E. C. K. Conner, M.A., Lecturer on 

 Economic Science, University College, Liverpool. 

 (London : George Bell and Sons, 1891.) 



I^HIS edition of Ricardo's " Principles " will be found 

 useful to students of political economy. In addition 

 to a large number of footnotes, the editor contributes an 

 introductory essay of forty pages, and two short ap- 

 pendices — (i) on Ricardo and his critics, (2) on the effect 

 upon rent of improvements in the fertility of land. The 

 introductory essay gives a general account and brief 

 critical estimate of Ricardo's work. It is characterized 

 NO. I 149, VOL. 45] 



by judicial moderation and impartiality ; and many am-^ 

 biguities and obscurities, due to the defects of Ricardo's 

 style, are cleared away. Naturally, the abstract theory 

 of value is treated first ; and here the editor acknow- 

 ledges that Ricardo did not attach sufficient importance 

 to the influence of demand in determinmg value. But, 

 on the serious question of the relation of capital to labour, 

 he hardly seems to make Ricardo's position clear. He 

 says (p. xxxix.) : — 



" Of course, the mere fact that capital is subject to 

 such replacements enables us to assert that, in the long 

 run, there is a tendency to some equality of reward be- 

 tween indirect labour {i.e. labour embodied in capital) 

 and direct labour. Thus in a somewhat abstract and 

 general way we may renew our previous statement that 

 commodities exchange in the ratio of their cost of 

 production." 



This passage, in which the editor concludes his general 

 criticism of Ricardo's theory of cost of production, appears 

 to involve the very fallacy that some SociaHsts have 

 committed in their reasonings based on Ricardo. For it 

 suggests their doctrine that capital is nothing but labour 

 applied indirectly to production. Now Ricardo most 

 explicitly avoided this fallacy. He wrote (p. 27) : — 



"On account of the time which must elapse before one 

 set of commodities can be brought to market, they will 

 be valuable, not exactly in proportion to the quantity of 

 labour bestowed on them, ... but something more to 

 compensate for the greater length of time which must 

 elapse" before the most valuable can be brought to 

 market." 



In short, Ricardo distinctly points out that an additional 

 value arises when the same quantum of labour is extended 

 over a larger period of lime. 



On the question of the distribution of reward between 

 capital and labour, the editor remarks (p. xxxviii.) :— 



" The two great agents in production— labour and 

 capital — so divide total value between them that an 

 increase in the value obtained by the one implies a 

 diminution in the share of value falling to the other." 



This apparently harmless truism is elaborated with 

 painful prolixity. But the form in which Ricardo ap- 

 plied it was always " Profits depend on wages "— never 

 " W^ages depend on profits." With Ricardo, profits were 

 the residue of production remaining over and above the 

 value of the standard of comfort ; and he did not enter 

 too closely into the question of the forces determining 

 variations in this standard. This crucial error shows 

 itself throughout all Ricardo's reasonings— notably in 

 his theory of taxation. 



In Appendix B, the treatment of the effects upon rent 

 of improvements in the fertility of land is very unsatis- 

 factory. The editor says that Ricardo made two assump- 

 tions—one implicitly and the other explicitly. But if he 

 had properly interpreted the assumption exphcitly made, 

 he would have seen that the other was unnecessary. 

 Ricardo explains quite clearly that the contemplated 

 improvement is assumed not to disturb " the difference 

 between the productive powers of the successive portions 

 of capital." The editor most gratuitously interprets dif- 

 ference to mean ratio, in the face of the fact that all 

 Ricardo's illustrations assume constancy of difference, 

 not constancv of ratio. Now Prof. Marshall has shown 



