Jan. 1, 1S6S.] 



HARDWICKE'S SCIENCE-GOSSIP. 



11 



THE USES OE VEGETABLE HAIRS. 



AS the leaves and stems of many plants, as well 

 as portions of their flowers, are covered with 

 innumerable minute hairs of many various forms, 

 it may be interesting to inquire what ends and uses 

 these hairs serve in the general economy of plant- 

 life ; for that they have some general use seems 

 clear from their frequent occurrence in many orders 

 of plants. And as the hairs of animals have one 

 general end — viz., warmth; but, coupled with this, 

 have other minor uses, such as ornament, conceal- 

 ment, and even defence against their foes — so in 

 the hairs which overspread the leaves and other 

 portions of plants, there seems to be one great 

 object for which they are designed; whilst other 

 objects of inferior value, but still important, are 

 readily observable, and indeed are sometimes more 

 obvious than that which appears to be the general one. 

 This end does not seem to be warmth,. or protection 

 from frost. Eor evergreens, which endure the frost, 

 are precisely those plants which possess the fewest 

 hairs ; and these distributed on that part of the 

 leaf which is least exposed to the severity of the 

 weather. Their chief object appears to be rather 

 to collect moisture from the air ; their ends afford- 

 ing innumerable points on which the minute drops 

 of dew may begin to distil. This is very apparent 

 on a frosty morning, when the little crystals of 

 frozen dew may be seen collected at the eud of 

 every hair of the leaves of such plants as the com- 

 mon buttercup, and others of the same kind. 



And this seems to be borne out by the fact that 

 most of the taller forest trees possess smoother 

 leaves than the greater part of the little plants 

 which cling to the surface of the earth, and are 

 often covered plentifully with hairs. As the taller 

 trees are, from the depth and abundance of their 

 roots, less exposed to the consequences of a short 

 drought than herbs, they do not need the same rapid 

 power of condensing dew which the herbs possess : 

 nor do they come so directly within its influences, 

 which are always the greatest, the nearest to the 

 ground. And evergreens, in which evaporation 

 from the surface is necessarily slow, are still more 

 independent of a moist atmosphere. Among these, 

 ivy has a few scattered hairs, indeed, which may 

 serve to draw some moisture, not only upon the 

 roots which penetrate the earth, but upon those 

 root-like processes by which it clings to trees and 

 rocks and walls. So that this exception would help 

 to prove the rule. And this seems to be true also 

 with respect to ferns ; for these possess but few 

 hairs, yet certainly delight in moisture, and flourish 

 best in damp and shady places. But still, except 

 some kinds, which grow best in the spray of a 

 waterfall, the moisture which seems most necessary 

 for them is that which their roots obtain from the 

 soil ; and as they are adapted to grow under the shade 



of rocks and trees, there is not the same necessity 

 for a quick distillation of moisture upon their 

 surfaces. 



As, then, the great majority of herbs do condense 

 dew upon their surfaces, and this is found chiefly 

 upon their hairs, it seems fair to conclude that one 

 great end why vegetables are clothed with hairs is 

 to bring about the deposit, of dew most rapidly. 



Besides this general use, there are others for 

 which some kinds of hairs are certainly designed. 

 Many terminate in glandular sacs containing some 

 strong-scented fluid, as in lavender, primula sinensis, 

 &c. These are frequently shorter than the ordinary 

 hairs, which are often so disposed as to form a pro- 

 tection to them, and so, perhaps, prevent a too rapid 

 dispersion of their scents. 



The sting of the nettle shows another modifica- 

 tion in the general structure of hairs. Here the 

 gland containing the poison is situated at the base 

 of the hair, which consists of one elongated cell 

 open at the end. Through this aperture the poison 

 escapes when the gland is gently pressed. In some 

 plants the hairs are so modified as to serve for the 

 purpose of climbing, as in the little hooks which 

 fringe the leaves of the common goose-grass. 



Again, the hairs which surround the throat of 

 many flowers seem designed to protect the nectary 

 from the intrusion of dust and other extraneous 

 matter, and so to preserve the honey pure, and also, 

 perhaps, by restraining evaporation, to keep it 

 sufficiently fluid. 



Other hairs, like the beautiful ones which clothe 

 the leaves of Deutzia scabra, seem, together with 

 their general office, to be designed for the orna- 

 mentation of the plant. 



Perhaps these few remarks may seem to draw 

 the attention of some of the readers of Science- 

 Gossip to this subject, whose observations may con- 

 firm or modify the views which is here taken of the 



general uses of Vegetable Hairs. 



J. S. Tttte. 



SPIDER NESTS. 

 {Theridion riparium.) 



"TVTOW, pray, lady reader,turn not from the folio w- 

 -*-^ ing hastily-arranged notes because they refer 

 to a creature so generally despised by the "fair sex " 

 as a spider. My object is to show you that in the 

 economy of this humble little being there is much 

 to interest the true lover of nature ; furthermore, 

 the subject of my gossip has nothing of a repulsive 

 character about it, being a tiny thing but about 

 the seventh of an inch long, and not at all ungraceful 

 in appearance. 



The cephalo-thorax (that portion of a spider to 

 which the legs are attached, and on the fore part of 

 which the eyes, mandibles, &c. are situated) is 



