588 



JOURNAL OF HOETICULTUEE AND COTTAGE GARDENER. 



[ December 31, 1874. 



shape of advertisements, &c., would be far preferable, as it 

 would not be likely to break, and I should fancy it would stand 

 any amount of weather. — Walter W. Bdenett. 



EAETHENWAEE COPING. 

 Its advantages are so evident that it seems to require no 

 notes from me, combining as it does a good permanent coping, 

 fruit-protector, and gutter to carry off the raiu. A slight slope 

 would, of course, be necessary, and a cast-iron shouldered pipe, 

 which I have indicated by dotted lines in the sketch, could 

 receive the water, and be carried down the wall into a sunken 

 tank. I should have the coping made of two sizes — viz., 

 2 feet 2 inches for a 9iueh wall, and 2 feet 6 inches for one of 

 14 inches. I fancy that it might be advisable, after fixing, to 



-SOt/i^ 



---> 



Kg. 165. 



paint the coping on the upper side and ends with " silicate 

 zopissa," or some other compound, to prevent the rain entering 

 the porous material, thereby giving a handle to the frost. I 

 should be glad, if any brickmakers (at whcae service I place it) 

 adopt it, if they would name it the " Emott Coping." — J. E. 



DO VARIETIES WEAR OUT, OR TEND TO 



WEAR OUT? 



Bi Pbofessof. Asa Gray. 



This question has been argued from time to time for more 

 than half a century, and is far from being settled yet. Indeed, 

 it is not to be settled either way so easily as is sometimes 

 thought. The result of a prolonged and rather lively discus- 

 sion of the topic about forty years ago in England, in which 

 Lindley bore a leading part on the negative side, was, if we 

 rightly remember, that the nays had the best of the argument. 

 The deniers could fairly well explain away the facts adduced 

 by the other side, and evade the force of the reasons then 

 assigned to prove that varieties were bound to die out in the 

 course of time. But if the case were fully re-argued now, it is 

 by no means certain that the nays would win it. The most 

 they could expect would be the Scotch verdict, "not proven." 

 And this not because much, if any, additional evidence of the 

 actual wearing-out of any variety has turned up since, but be- 

 cause a presumption has been raised under which the evidence 

 would take a bias the other way. There is now in the minds 

 of scientific men some reason to expect that certain varieties 

 would die out in the long run, and this might have an impoi- 

 tant influence upon the interpretation of the facts that would 

 be brought forward. Curiously enough, however, the recent 

 discussions to which our attention has been called seem on 

 both sides to have overlooked this matter. 



Some varieties may disappear or deteriorate, but yet not 

 wear out — not come to an end from any inherent cause. One 

 might even say, the younger they are the less chance of sur- 

 vival unless well cared for. They may be smothered out by 

 the adverse force of mere superior numbers ; they are even 

 more likely to be bred out of existence by unprevented cross- 

 fertilisation, or to disappear from mere change of fashion. 

 The question, however, is not so much about reversion to an 

 ancestral state or the falUng-off of a high-bred stock into an 



inferior condition. Of such cases it is enough to say thaH 

 when a variety or strain of animal or vegetable is led up to 

 unusual feoundity or size or product of any organ, for our good, 

 and not for the good of the plant or animal itself, it can be 

 kept so only by high feeding and exceptional care ; and that 

 with high feeding and artificial appliances come vastly in- 

 creased liability to disease, which may practically annihilate 

 the race. Eat then the race, like the bursted boiler, could not 

 be said to wear out ; while if left to ordinary conditions, and 

 the race allowed to degenerate back into a more natural ii 

 less useful state, its hold on hfe would evidently be increased 

 rather than diminished. 



As to natural varieties or races under normal conditions 

 sexually propagated, it could readily be shown that they are 

 neither more nor less likely to disappear from any inherent 

 cause than the species from which they originated, upon which, 

 indeed, only vague conjectures can be offered. The matte? 

 actually under discussion concerns cultivated or domesticated 

 varieties only. 



First, will races propagated by seed, being so fixed that they 

 come true to seed, and purely bred (not crossed with any 

 other sort), continue so indefinitely, or will they run out in 

 time — not die out, perhaps, but lose their distinguishing charac- 

 ters? Upon this, all we are able to say is that we know no 

 reason why they should wear out or deteriorate from any in- 

 herent cause. The transient existence or the deterioration 

 and disappearance of many such races are sufiieiently accounted 

 for otherwise. As in the case of extraordinarily exuberant 

 varieties, such as mammoth fruits or roots, by increased 

 liability to disease, already adverted to, or by the failure of 

 the high feeding they demand. A common cause, in ordinary 

 cases, is cross-breeding through the agency of wind or insects, 

 which is difficult to guard against. Or they go out of fashion 

 and are superseded by others thought to be better, and so the 

 old ones disappear. 



Or finally, they may revert to an ancestral form. As ofi- 

 spring tends to resemble grand-parents almost as much as 

 parents, and as a line of close-bred ancestry is generally pre- 

 potent, so newly originated varieties have always a tendency to 

 reversion. This is pretty sure to show itself in some of the 

 progeny of the earlier generations, and the breeder has to 

 guard against it by rigid selection. But the older the variety 

 is — that is, the longer the series of generations in which it has 

 eome true from seed — -the less the chance of reversion : for now, 

 to be like the immediate parents, is also to be like a long line 

 of ancestry ; and so all the influences concerned — that is, both 

 parental and ancestral heritability — pull in one and the same 

 direction. So, since the older a race is the more reason it has 

 to continue true, the presumption of the unlimited perma- 

 nence of old races is very strong. 



Of course the race itself may give off new varieties ; but that 

 is no interference with the vitality of the original stock. Ii 

 some of the new varieties supplant the old, that will not be 

 because the unvaried stock is worn out or decrepid with age, 

 but because in wild nature the newer forms are better adapted 

 to the surroundings, or, under man's care, better adapted to his 

 wants or fancies. 



The second question, and the one upon which the discus- 

 sion about the wearing-out of varieties generally turns, is, Will 

 varieties propagated from buds — i.e., by division, grafts, bulbs, 

 tubers and the like, necessarily deteriorate and die out ? First, 

 Do they die out as a matter of fact ? Upoa this, tha testimony 

 has all along been conflicting. Andrew Knight was sure that 

 they do, and there could hardly be a more trustworthy witness. 



"The fact," he says, fifty years ago, " that certain varieties 

 of some species of fruit which have been long cultivated can- 

 not now be made to grow in the same soils and under the same 

 mode of management which was a century ago perfectly suc- 

 cessful, is placed beyond the reach of controversy. Every 

 experiment which seemed to afford the slightest prospect of 

 success was tried by myself and others to propagate the old 

 varieties of the Apple and Pear which formerly constituted the 

 orchards of Herefordshire, without a single healthy or efficient 

 tree having been obtained ; and I believe all attempts to propa- 

 gate these varieties have, during some years, wholly ceased to 

 be made." 



To this it was replied, in that and the next generation, that 

 cultivated Vmes have been transmitted by perpetual division 

 from the time of the Romans, and that several of the sorts, 

 still prized and prolific, are well identified, among them the 

 ancient Grseoula, considered to be the modern Corinth or 

 Currant Grape, which has immemorially been seedless ; that 



