March 2, 1885.] 



THE TROPICAL AGRICULTURIST. 



693 



tion to this diagram, showing how the branching of the 

 root proper is brought about. In the interior of the 

 growing root a number of cells begin to multiply at 

 certain points, and to form the young beginnings of lateral 

 roots or rootlets ; further back you see these young lateral 

 roots upheaving the tissues of their parent root as minute 

 knobs. By this time, however, these portions of the mother 

 root have ceased to grow in length, and thus the tender 

 little tips of the lateral roots can protrude and be 

 pushed into the soil around without danger of being 

 dragged off or injured, as they would inevitably be if this 

 part of their mother root were still actively elongating. 

 Notice carefully the exquisite adaptation to the circum- 

 stances, though brought about in a slightly different manner ; 

 no time is lost in the preparation of the young root 

 branches within the tissues of the parent root, but the 

 tender tips, as in the case of the root-hairs, only pro- 

 ceed to grow radially into the surrounding soil when 

 the growth of the mother root in a direction across 

 their long axes has ceased. 



Time will not allow of our examining these matters 

 more in detail; but I cannot avoid calling your attention 

 to the fact that these lateral roots are sensitive to gravitation 

 in a manner different from the primary root — they grow, 

 not straight down towards the centre of the earth, but 

 across the vertical, it may be more or less inclined, in 

 different cases. In other respects they resemble the 

 primary root generally, in their turn producing root-hairs 

 and daughter roots, which radiate from them iu all direc- 

 tions into new portions of the soil, as shown in this 

 diagram. 



I need not do more than point out to you that it would 

 be difficult to conceive of a series of adaptations better 

 calculated to insure that the various parts of the root- 

 system come successively in contact with the whole mass 

 of soil traversed; and when your eyes follow mine over 

 this diagram, you will agree that matters have become 

 so arranged, so to speak, between the roots and the 

 soil, that every part of the latter is laid under contrib- 

 ution. Notice how this vertical cylinder of earth is first 

 bored through by the primary root, and then traversed in 

 all directions by the root-hairs, iu a wave, as it were, 

 passing from above downwards. Next come the lateral 

 roots, burrowing iu all directions from the main shaft, 

 and each in turn demanding toil from the cylinder 

 around it by means of its wave of root-hairs. Then 

 follow tunnelings along the lengths of each of these 

 rootlets, and on all sides at right angles to them, until 

 every nook and cranny has been investigated by these 

 enterprising rootlets and their prying root-hairs. Quite 

 apart from all else, therefore, the root-system obtains a 

 greater holdfast on the soil by driving its tips in on all 



But I must now draw your attention to some matters 

 which throw even more light on our subject. The root- 

 hairs, as they develop successively from 'above downwards 

 on the primary root, or on the lateral rootlets, come into 

 the closest contact with the particles of soil — contact so 

 close and firm, in fact, that they cannot be torn away 

 without injury. There are experiments to prove that their 

 cellulose walls become actually moulded and gummed on 

 to the solid particles of quartz, slate, and other rocks 

 of which ordinary soils are composed, and this diagram 

 shows how we can lift up a relatively large cylinder of 

 soil adhering to the root-hairs of a young seedling. 



Now you are probably aware that the sort of soil in 

 which a healthy plant nourishes contains air-bubbles as 

 well as water in the interstices between the particles, 

 and into which the root-hairs become insinuated. Bear- 

 ing this in mind, you will have no difficulty in under- 

 standing from the diagram how root-hairs absorb the 

 aerated water necessary for their well-being. I need 

 simply make the additional remark that each little bag- 

 like root-hair takes up the liquid water through its per- 

 meable walls into its interior, in some respects very much 

 sa a bladder full of a solution of sugar or salt absorb water if 

 placed in it. 



But this water taken up by the root-hairs and passed 

 on into the rootlets and so on up the stem (a process 

 for which provisions are made which we cannot go into 

 here), is not pure water; it contains, besides air, certain 

 small proportions of the soluble matters found iu all 



soils. It is, in fact, much like ordinary drinking-watt* 

 from a well or spring, which always contains some matters 

 in solution. But the roots want certain other minerals, 

 which will not dissolve in pure water to a sufficient ex- 

 tent under the ordinary circumstances. Well, the root- 

 hairs, in making use of the oxygen which they, like all 

 other living bodies, require, give off small quantities of 

 acids which aid the solution of these more refractory 

 matters. 



And now I have finished— not because the subject is 

 exhausted, but because the time at our disposal is. I 

 hope the object has been attained, and that you fully 

 realise how well worthy of study is a common living root. 

 Not only is it instructive as a simple object of dissection, 

 a subject upon which I have had no time to dwell, 

 but the peculiar properties which stamp it as a living 

 organ themselves afford material for much thought and 

 investigation. When we go further, however, and see 

 how the structure and the functions depend upon one 

 another, some very curious reflections thrust themselves 

 upon us; and if time had allowed us to look at these 

 matters from the other platforms of view — to see how 

 old errors have gradually been explained away on the part 

 of observers, and how what may be called improved 

 adaptations have arisen in the evolution of the root as 

 an organ — these reflections would have obtained in depth. 

 But we have taken a glimpse at matters still more com- 

 prehensive: we have touched upon that important ques- 

 tion of the relation of the root to its physical environ- 

 ment, and it is not difficult to see numerous points 

 where the struggle must have been intense before the 

 plastic substance of the root wa,s enabled to meet the 

 requirements necessary before it could become a dweller 

 in the land. The evidence of progress and adaptation to 

 its environment on the part of the root is, in fact, so 

 striking and conclusive, that we might take it as a text 

 for a sermon on evolution were such necessary. I have 

 been strongly tempted to occupy some more time with 

 reference to the interesting phenomena shown by roots 

 which cling to trees and walls, &c., or which rob other 

 plants of food-materials; and had time allowed, I would 

 have liked to say a few words about some other adapt- 

 ations, such as those by means of which roots become 

 pulled up taut in the soil. However, these and other 

 matters cannot be even mentioned, and, indeed, each one 

 deserves a lecture to itself. — Nature. 



BEOHE-DE-MER FISHINC. 



BY WILFKED POWELL, F.R.G.S. 



Beche-de-mer (also called Biche-de-mer, Tripaug, Trepang, 

 Sea-cucumber, or Sea-slug, terms applied to various species 

 of the genus Holothuria) is an article of food apparently 

 little known to epicures in this country, although, I be- 

 lieve, it has of late years become a dish of much popul- 

 arity amongst the wealthier classes in France ; and Delle 

 Chiaje some forty years ago said that Holothurians were 

 eaten by the poor inhabitants of the Neapolitan coasts. 

 It has, however, been for ages highly esteemed as one 

 of the greatest delicacies prepared for the table of the 

 enervated upper classes in China; indeed, even a poorer 

 Chinaman will often go without some more necessary 

 article in order to indulge in his favourite dish. Its 

 appearance is certainly not calculated to give a very 

 keen edge to the appetite, being as much like a huge 

 slug as anything. 



I propose in this article to give some account of the 

 existing beche-de-mer industry. Anoyne desiring to 

 become acquainted with the leading physical characteris- 

 tics of the animal, and its position iu scientific classific- 

 ation, will find those points discussed by Mr. P. H. Carpen- 

 ter in vol. vi. of Cassell's "Natural History," edited by 

 Professor Martin Duncan, a work accessible to all. It 

 might suffice here to say that the genus Holothuria forms 

 with Cucumaria, Psolus, &c, an order, Pedata, included 

 in the class Holothuroidea of the Echinodermata. We 

 have some Holothurians on our own coasts, and aoout 

 thirty-five different varieties are enumerated by Chinese 

 traders, though only about five or six have any commercial 

 value. An account of these is to be found in Simmonds's 

 •'Commercial Products of the Sea." by Oapt. Andrew 



