HARDWICKE'S SC1EN CE-G0SS1P. 



59 



seen perfectly denuded thereof; for no sooner do 

 the old ones drop than fresh ones appear ;— hence 

 in such a sense it is evergreen. 



What makes me attach still more importance to 

 the effects which flowering and fruiting have in 

 partly aiding defoliation, is due to the case of a 

 tree, possessed by a friend of mine, coming under 

 my notice only a short time ago. This tree, which 

 he has had now for close upon four years, has never 

 parted with a leaf during the whole of the time, 

 yet looks as healthy and vigorous as ever it did. 

 Now I cannot account for this on any other ground 

 than that of its never having flowered in the time. 

 Certainly the plant is not elbow-jointed where the 

 leaves join the stem ; still I cannot see how this can 

 well be accepted as a main cause. Then there is the 

 question of articulation to be considered as effecting 

 defoliation. This ought not, as some seem to do, to 

 be regarded as fully causative. It may, and indeed 

 no doubt does, after the sap becomes less active 

 through the chilling influence of cold, or other 

 causes, induce the leaves to fall more rapidly ; still 

 even this would be very much dependent on the 

 nature of the wood of the plant. To mention a case 

 as illustrative of this point, I would allude to the 

 beech— a tree, among others, that retains its leaves 

 in a decayed condition throughout the winter, even 

 to the shooting of the buds. Now I am so bold as 

 to think that even their points of attachment would 

 become very much strengthened could but the 

 vitality of the leaves be maintained beyond a year 

 or so under favourable climatical influences. 



Then as to trees, there is another thing which 

 ought not to be lost sight of in the consideration of 

 this subject. I refer to their height, and the in- 

 creased coldness to which the leaves are as a conse- 

 quence subjected, all which must have, and espe- 

 cially in cases where the leaves are tender and 

 gifted with " free lungs," a very great influence in 

 hastening and prolonging their nudity. In proof 

 of this witness the effects of a mild winter; for 

 scarcely will vegetation have had time to replenish 

 itself from the impoverishing effects of fruiting 

 before the activity of the sap will be again mani- 

 festing itself through the appearance of buds, 

 showing how cold keeps in abeyance the sap, and 

 chiefly through that causes defoliation and length- 

 ened nudity, and also where in some instances it 

 has reached the plant in its most sheltered parts — 

 the roots— it has killed it altogether. 



Perennials, or those in which such phenomena as 

 defoliation, &c, take place, are for the most part 

 ligneous or subligneous in their structure ; and de- 

 pending upon this is their power of endurance and 

 resistance. Hence I take it that the leaves, flowers, 

 and fruits, together with their petioles and pe- 

 duncles, being chiefly made up of a softer tissue, 

 are sooner perishable, and as a consequence fall 

 away. Especially so does this appear in a measure 



partly explanatory of such phenomena, when we 

 don't find, as a rule, such appearance occurring 

 amongst plants which are herbaceous, or, in other 

 words, those in which the parenchymatous system 

 predominates throughout; as in these we find all 

 equally perishing throughout, without any such sepa- 

 ration of parts. Apparently confirmatory of this 

 we will take the effects of a keen prolonged frost 

 upon newly-formed wood or young branches ; the 

 result being that of its becoming nipped, giving rise 

 to what here might also be equally and feasibly 

 claimed as the " Phenomenon of Delignization." 



As to what appropriate warmth, soil, and moisture 

 will do in keeping up the vitality and foliage of 

 plants generally, we have well exemplified at home 

 in our nurseries, where a case of complete plant- 

 nudity would rarely or ever be witnessed. We have 

 but to study the geographical distribution of plants 

 in order to gain a correct knowledge of how far 

 soil and climate go towards influencing vegetable 

 growth. If, for instance, we were to go to Egypt, 

 we should there find plants going through the 

 phases of their existence in one half the time 

 they do here. But, on the other hand, we 

 should find, as we proceeded from warmer regions 

 towards the poles, that, as the light and heat 

 diminished, the vegetation is checked in the same 

 proportion ; proving that it is only where the sun 

 rises highest in the ever-cloudless heavens that vege- 

 tation flourishes in the greatest luxuriance, and 

 assumes its most majestic form. 



I hope that this imperfect paper may be the 

 means towards eliminating something further on 

 this most interesting subject through the pages c f 

 Science-Gossip. 



Sheffield. John Harrison. 



EXOTIC ENTOMOLOGY.* 



THERE are few living authors who have intro- 

 duced more students to the various branches 

 of natural science than the Rev. J. G. Wood. As 

 an author he has the happy knack of immediately 

 striking a friendship with his readers, unless, indeed, 

 they are more captious than usual. The entire 

 field of zoology has been roamed over by him, and 

 there is hardly one of its corners he has not explored. 

 The wonder is, not that amidst so many books 

 written by one man, there should be some errors in 

 fact and errors in judgment, but that there are so 

 few. If there is a tendency sometimes to dismiss 

 those leading speculations which are agitating the 

 minds of the best and most philosophical naturalists 

 in the world, somewhat contemptuously, it is because 



* " Insects Abroad ; being a Popular Account of Foreign 

 Insects." By the Rev. J. G. Wood, M.A., F.L.S. London: 

 Longman, Green, & Co. 1874. 



