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Show 20 INTRODUCTORY REMARKS. CnAI>. I. flowers on one or more of the crossed plants were fertilised with pollen from another crossed plant of the sa1ne lot. Having thus once begun, th~ sam m t?od was followed for as many as ten successive gen rat1on with some of the species. The seeds and seedlings \Yere always treated in exactly the same mann r as .al: ady described. The self-fertilised plants, wh th r ono-1nally descended from one or two mother-plant , w r thus in each generation as closely interbred as was possible; and I could not have improved on my })h n. But instead of crossing one of the crossed plants with another crossed plant, I ought to have crossed the selffertilised plants of each generation with I 11 n taken fron1 a non-related plant-that is, one belonging to a distinct family or stock of the same speci s and variety. This was done in several cases as an additional xpcriInent, and gave very striking results. But th plan usually followed was to put into comp tition and compare intercrossed plants, which w r almost always the offspring of more or less closely relat d plant , with the self-fertilised plants of each succeeding g neration ;-all having been grown under cl s ly sin1ilar conditions. I have, however, learnt more by this method of proceeding, which was begun by an v rsight and then necessarily followed, than if I had always crossed the self-fertilised plants of each succeeding generation with pollen from a fresh stock. I have said that the crossed plants of the successiYe generations were almost always inter-relat d. \Vhen the flowers on an hermaphrodite plant are crossed with pollen taken from a distinct plant, the seedlings thus raised may be considered as hermaphrodite brothers or sisters ; those raised from the san1e capsule being as close as twins or animals of the same litter. But in one sense the flowers on the sa1ne plant are distinct C HAP. I. INTRODUCTORY REMARKS. 21 individuals, and as several flowers on the mother-plant were crossed by pollen taken from several flowers on the father-plant, such seedlings would be in one sense half-brothers or sisters, but more closely related than ~re the half-brothers and sisters of ordinary animals. The flowers on the n1other-plant were, however, commonly crossed by pollen taken fron1 two . or more distinct plants ; and in these cases the seedlings might be called with more truth half-brothers or sisters. vVhen two or three mother-plants were crossed, as often happened, by pollen taken from two or three fatherplants (the seeds being all intermingled), some of the seedlings of the first generation would be in no way related, whilst many others would be whole or halfbrothers and sisters. In the second generation a large number of the seedlings would be what may be called whole or half first-cousins, mingled with whole and half-brothers and sisters, and with some plants not at a_ll related. So it would be in the succeeding generations, but there would also be many cousins of the second and more remote degrees. The relationship will ~hus have become more an~ more inextricably complex In the later generations; with most of the plants in some degree and many of them closely related. I have only one other point to notice, but this is one of the highest importance; namely, that the crossed and self-fertilised plants were subjected in the same generation to as nearly similar and uniform conditions as was possible. In the successive generations they were exposed to slightly different conditions as the seasons varied, and they were raised at different periods. But ~n other respects all were treated alike, being grown In pots in the same arti:ficiall y prepared soil, being watered at the same time, and kept close together in the same greenhouse or hothouse. They were |