1884.] TREES : THEIR FORMS, ETC. 281 



or wlieat. He writes : ' We traced the sometimes total loss of the 

 crop of trifoliwn to this source, inasmuch as we fouad the insects in 

 the top joint of the stubble, among which we usually drilled the 

 Trifolium incaniatuni without ploughing. We lightly skimmed the 

 stubble, and so deprived the weevil of its habitat and refuge, and we 

 believe we abated the evil.' In the cases where the clover is "rowin". 

 the proper preventive of attack still needs to be found. We cannot 

 put on the killing dressings which are suitable to land before break- 

 ing up ; but, still, lesser dressings of the same chemical applications, 

 such as lime or gas lime, would do some good by making the ground 

 less fit for egg-laying, and also by choking up many of the hollow 

 stems of stubble, so that the weevils could not get down them for 

 their winter rest. Gas lime in proper amount (that is, as a fertilizer, 

 not a destroyer) would be particularly likely to do good, as being 

 obnoxious to the insect, and also (as being merely another form of 

 gypsum) it would tend to promote the healthy growth of the clover. 

 Whether, as we learn more about the workings of these maggots, we 

 shall find that what has hitherto passed und^r the name of clover 

 sickness may be in part owing to the plant failing from loss of a part 

 of its roots, and decay of what was left in consequence of unsuspected 

 maggot attack, as well as the purely vegetable disease, remains to be 

 seen ; but in either case the application of gas lime, of course properly 

 exposed to atmospheric action previously, would be of use. 



TREES : THEIR FORMS AND LAWS OF GROWTH. 



^HE vegetable kingdom, which comprises all the subjects of 

 which botany takes cognisance, has been roughly divided into 

 trees, shrubs, flowers, iiowerless plants, and fossils. The 

 division is convenient though arbitrary, and useful though unscien- 

 tific. It is based on the general form, size, and consistence of plants, 

 and we not do hesitate to speak of trees as though some of them 

 are not gigantic shrubs. In doing so we notice two well-developed 

 types of tree: the one tall of stem, columnar, with few branches, 

 and these chiefly at top ; the other bushy, spreading, somewhat round 

 in contour, and with many Ijrauches. The first is essentially a timber 

 tree ; the second is essentially a huge shrub. Both types result from 

 the operation of certain laws of nature called laws of growth. These 

 laws, as we shall see by-and-by, do not cease to be laws of growth 

 on our discovering their physical origin. Indeed, if from the sum 

 total of our knowledge of the laws of growth we were to deduct 

 the sum of our knowledge of physical laws that enter into it, the 

 remainder would scarcely be sufficient to show our ignorance of that 



u 



