January 6, 1892.] 



Garden and Forest. 



to the whole number of individuals. That is, the hybrids are 

 rare, while the parents may be common. 



Darwin was the first to show that crossing within the limits 

 of the species or variety results in a constant revitalizing of the 

 offspring, and that this is the particular ultimate function of 

 the operation. Darwin's results are, concisely, these : self- 

 fertilization tends to weaken the offspring ; crossing between 

 different plants of the same variety gives stronger and more 

 productive offspring than arises from self-fertilization ; cross- 

 ing between stocks of the same variety grown in different 

 places, or under different conditions, gives better offspring 

 than crossing between different plants grown in the same 

 place or under similar conditions ; and his researches have 

 also shown that, as a rule, Howers are so constructed as to 

 favor cross-fertilization. In short, he found, as he expressed 

 it, that " nature abhors perpetual self-fertilization." Darwin's 

 well-known experiments show that crosses between fresh stock 

 of the same variety were nearly thirty per cent, more vigorous 

 than crosses between plants grown side by side for some time, 

 and over forty-four per cent, more vigorous than plants frorii 

 self-fertilized seeds. On the other hand, experiments showed 

 that crosses between different flowers upon the same plant gave 

 actually poorer results than offspring of self-fertilized flowers. 

 It is evident, from all his experiments, that nature desires 

 crosses between plants, and, if possible, between plants grown 

 under somewhat different conditions. 



In extended experiments of my own in the crossing of 

 Pumpkins, Squashes and Gourds, carried on during sev- 

 eral years, increase in productiveness due to crossing has 

 been marked in many instances. Marked increase in produc- 

 tiveness has been obtained from Tomato crosses, even when 

 no other results of crossing could be seen. 



NEW CHARACTERS FITTED TO NEW CONDITIONS. 



- Almost every farmer and gardener at the present day feels 

 that an occasional change of seed results in better crops. 

 Much of the rapid improvement in fruits and vegetables in 

 recent years is due to the pracdce of buying plants and seeds 

 so largely of dealers, by means of which the stock is often 

 changed. Even a slight change, as between farms or neigh- 

 boring villages, sometimes produces more vigorous plants and 

 often more fruitful ones. In the cross, a new combination of 

 characters or a new power fits it to live better than its parents 

 in the conditions under which they lived. In the case of 

 change of stock we find just the reverse, which, however, 

 amounts to the same thing, that the new characters or powers 

 fit the plant to live better in conditions new to it than plants 

 which have long lived in those conditions. In either case the 

 good comes from the fitting together of new characters or 

 powers and new environments. 



Crossing within the variety and change of stock within ordi- 

 nary bounds are therefore beneficial, and the results in the two 

 cases seem to flow from essentially the same causes, and 

 crossing and change of stock combined give much better re- 

 sults than either one alone. These processes are much more 

 important than any mere groping after new varieties, not only 

 because they are surer, but because they are universal and 

 necessary means of maintaining and improving both wild and 

 cultivated plants. Upon this point Darwin expressed himself 

 as follows: " It is a common practice with horticulturists to 

 obtain seeds from another place having a very different soil, 

 so as to avoid raising plants for a long succession of genera- 

 tions under the same conditions ; but with all the species 

 which freely intercross by the aid of insects or the wind, it 

 would be an incomparably better plan to obtain seeds of the 

 required variety, which had been raised for some generations 

 under as different conditions as possible, and sow them in 

 alternate rows with seeds matui^d in the old garden. The two 

 stocks would then intercross with a thorough blending of 

 their whole organizations, and with no loss of purity to the 

 variety ; and this would yield far more favorable results than 

 a mere change of seeds." 



PRODUCING NEW PLANTS. 



The second result of crossing, the summary production of 

 new varieties, is the subject which is almost universally asso- 

 ciated with crossing in the popular mind, and even among 

 horticulturists themselves. It is the commonest notion that 

 the desirable characters of given parents can be definitely com- 

 bined in a pronounced cross or hybrid. There are two or 

 three philosophical reasons which somewhat oppose this doc- 

 trine, and which we will do well to consider at the outset. In 

 the first place, nature is opposed to hybrids, for species have 

 been bred away from each other in the ability to cross. If, 

 therefore, there is no advantage for nature to hybridize, we 



may suppose that there would be none for man ; and there 

 would be no advantage for man did he not place the plant un- 

 der conditions different from nature or desire a different set of 

 characters. We can overcome the refusal to cross in many 

 cases by bringing the plant under cultivation where new con- 

 ditions overpower its former antipathies. Yet it is doubtful if 

 such a plant will ever acquire a complete willingness to cross. 

 In like manner we can overcome in a measure the compara- 

 tive seedlessness of hybrids, but it is very doubtful if we can 

 ever make such hybrids completely fruitful. It would appear, 

 therefore, that with plants in which fruits or seeds are the parts 

 sought, no good can be expected, as a rule, from hybridizafion, 

 and this seems to be affirmed by facts. It is evident that spe- 

 cies which have been bred away from each other in a given 

 locality will have more opposed qualities than similar species 

 which have arisen quite independently in places remote from 

 each other. In the one case the species have struggled with 

 each other until each one has attained to a degree of diver- 

 gence which allows it to persist, while in the other case there 

 has been no struggle between the species, but similar condi- 

 tions have brought about similar results. These similar spe- 

 cies which appear independently of each other in different 

 places are called representative species. Islands remote from 

 each other, but similarly situated with reference to climate, 

 very often contain such species, and the same may be said of 

 other regions much like each other. Now it follows that if 

 representative species are less opposed than others, they are 

 more likely to hybridize with good results ; and this fact is well 

 illustrated in the Kieffer and allied Pears, which are hybrids 

 between representative species of Europe and Japan. We will 

 also recall that the hybrid Grapes which have so far proved 

 most valuable are those obtained by Rogers between the 

 American Vitis Labrusca and the European Wine Grape, and 

 that the attempts of Haskell and others to hybridize associated 

 species of native Grapes have given, at best, only indifferent 

 results. 



HYBRIDS RARE AND UNSTABLE. 



Another theoretical point borne out by practice is that be- 

 cause of the great differences between parents, pronounced 

 hybrid offspring are unstable. Again, because of the unequal 

 and unknown powers of the parents, we can never predict what 

 characters will appear in the hybrids. This fact was well ex- 

 pressed by Lindley a half century ago in the phrase, " Hybri- 

 dizing is a game of chance played between man and plants." 

 The characters of hybrids as compared with the characters of 

 simple crosses between stocks of the same variety are there- 

 fore ambiguous, negative and often prejudicial. 



The difficulties in the way of successful results through 

 hybridization are, therefore, the difficulty of effecting the 

 cross, infertility, instability, variability, and often weakness 

 and monstrosity of the hybrids, and the absolute impossibility 

 of predicting results. The advantage to be derived from a 

 successful hybridization is the securing in combination the 

 most desirable features of both parents ; and this advantage 

 is often of so great moment that it is worth while to experi- 

 ment in the face of numerous failures. From theoretical con- 

 siderations it is apparent that hybridization is essentially an 

 empirical subject, and the results are such as fall under the 

 common denomination of chance. And as it does not rest 

 upon any legitimate function in nature, we can understand 

 that it will always be difficult to codify laws upon it. 



Among the various characters of hybrid-oftspring, the most 

 prejudicial one is their instability ; it is difficult to fix any par- 

 ticular form which we may secure in the first generation of 

 hybrids ; and, therefore, we find that the great majority of the 

 best hybrids in cultivation are increased by bud-propagation, 

 as cuttings, layers, suckers, buds or grafts. In fact, there are 

 few instances of undoubted hybrids which are propagated 

 with practical certainty by means of seeds. 



This siniply means that it is difficult to fix hybrids so that 

 they will come "true to seed," and makes apparent the fact 

 that if we desire hybrids we must expect to propagate them 

 by means of buds. 



Let us now recall how many undoubted hybrids there are, 

 named and known, among our fruits and vegetables. In 

 Grapes there are the most. There are Rogers' hybrids, like 

 Agawam, Lindley, Wilder, Salem and Barry ; and there is some 

 reason for supposing that Delaware, Catawba and other varie- 

 ties are of hybrid origin. And many hybrids have come to 

 notice lately through the work of Munson and others. But it 

 must be remembered that Grapes are naturally exceedingly 

 variable, and the specific limits are not well known, and that 

 hybridization among them lacks much of that definiteness 

 which ordinarily attaches to the subject. In Pears there is the 



