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Show 196 PE'rUNIA VIOLACEA. CHAP. VI. crossed offspring. It is unfortunate that I did not turn these plants out of doors, so as to obse1·ve their relative fertility, for I compared the pollen from some of the crossed and self-fertilised plants in Pot I., Table LXXXI., and there was a marked difference in its state; that of the· crossed plants contained hardly any bad and empty grains, whilst such abounded in the pollen of the self-fertilised plants. The Bjfects of a Cross with a fnsh Stoclc.-I procured from a garden in Westerham, whence my plants originally came, a fresh plant differing in no respect from mine except in the colour of the flowers, which was a fine purple. But this plant must have been exposed during at least four generations to very different conditions from those to which my plants had boon subjected, as these had been grown in pots in the greenhouse. Eight flowers on the self-fertilised pla,nts in Table LXXXI., of the last or fourth self-fertilised generation, wore fertilised with pollen from this fresh stock; all eight produced capsules containing together by weight 5 · 01 grains of seeds. The plants raised from these seeds may be called the TVe.~terhamcrossed. Eight flmvers on the crossed plants of the last or fourth generation in Table LXXXI. were again crossed with pollen from one of the other crossed plants, and produced five capsules, containing by weight 2 · 07 grains of seeds. The plants raised from these seeds may be called the intercrossed; and these form tho fifth jntercrossed generation. Eight flowers on the self-fertilised plants of the same generation in Table LXXXI. were again self-fertilised, and produced seven capsules, containing hy weight 2 ·1 grains of seeds. The self-fer·Ulised plants raised from these seeds form the fifth selffertilised generation. These latter plants and the intercrossed are comparable in all respects with the crossed and self-fertilised plants of the four previous generations. From the foregoing data it is easy to calculate that, Gr. Weight of Seed. Ten \Vesterham-crossed capsules would have contained G·:26 Ten inter crossed capsules would have contained . 4 ·14 Ten self-fertilised capsules would have contained 3·00 ""Ne thuFl get the following ratios:- CHAP. VI. CROSS WITH A FRESH STOCK. Seeds from the Wester bam-crossed capsules to those from the capsules of the fifth self-fer- 197 tilised generation, in weight, as 100 to 48 Seeds from the Wester ham-crossed capsules to those from the capsules of the fifth in tercrossed generation, as 100 to 66 Seeds from the intercrossed to those from the self-fertilised capsules, as 100 to 72 So that a cross with pollen from a fresh stock greatly increased the productiveness of the flowers on plants which had been selffertilised for the four previous generations, in comparison not only with the flowers on the same plants self-fertilised for the fifth time, but with the flowers on the crossed plants crossed with. pollen from another plant of the same old stock for the fifth time. These three lots of seeds were placed on sand, and were planted in an equal state of germination in seven pots, each made tripartite by three superficial pa,rtitions. Some of the remaining seeds, whether or not in a state of germination, were thickly sown in an eighth pot. The pots were kept in the greenhouse, and the plants trained up sticks. They were first measured to the tops of their stems when coming into flower ; and the twentytwo Wester ham-crossed plants then averaged 25 ·51 inches; the twenty-three intercrossed plants 30 · 38; and the twenty-three self-fertilised plants 23 · 40 inches in height. We thus get the following ratios :- The Westerham-crossed plants in height to the self-fertilised . . as 100 to 91 The W esterham-crossed plants in height to the intercrossed . . . . as 100 to 119 The intercrossed plants in height to the self-fertilised . . as 100 to 77 These plants were again measured when their growth appeared on a casual inspection to be complete. But in this I was mistaken, for after cutting them down, I found that the summits of the stems of theW ester ham-crossed plants were still growing vigorously; whilst the intercrossed had almost, and the selffertilised had quite completed their growth. Therefore I . do not doubt, if the three lots had been left to grow for another month, that the ratios would have been somewhat different |