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Show 188 PETUNIA VIOLACEA. CHAP. VI. CHAPTER VI. SoLANAOElE, PmMULAOEJE, PoLYGONElE, ETC. Petunia violacea, crossed and self-fertilised plants compared for four generations-Effects of a cross with a fresh stock- Uniform colom of the flowers on the self-fertilised plants of the fo,Irtll generation -Nicotiana tabacum, crodsed and self-fertilised plants of eq nal height-Great effects of a cross with a distinct sub-variety on the height, but not on the fertility, of the offspring-Cyclamen persicum, crossed seedlings greatly superior to the self-fcrtili sedAnagallis collina-Primula veris-Equal-styled variety of Primula veris, fertility of, greatly increased by a cross with a fresh stockFagopyrum esculentum-Betu. vulgaris-Canna wurscowiczi, crossed and self-fertilised plants of equal height-Zea mays-Phalaris cn,nariensis. XXV. SOLANA.CEJE.-PETUNIA VIOLAOEA. Dingy purple variety. THE fLowers of this plant are so seldom visited during the day by insects in this country, that I have never seen an instance; but my gardener, on whom I can rely, once saw some humblebees at work. Mr. Meehan says,* that in the United States bees bore through the corolla for the nectar, and adds that their "fertilisation is carried on by night-moths." In France M. Naudin, after castrating a large number of.fiowers whilst in bud, loft them exposed to the visits of insects, and about a quarter produced capsules ;t but I am convinced that a much larger proportion of flowers in my garden are crossfertilised by insects, for protected flowers with their own pollen placed on the stigma never yielded nearly a full complement of seed; whilst those left uncovered produced fine capsules, showing that pollen from other plants must have been brought to them, probably by moths. Plants growing vigorously and fLowering in pots in the green-house, never yielded a single ca psulo ; and * 'Pro c. Acad. Nat. Sc. of Philadelphia,' Aug. 2nd, 1870, p. 90. t 'Annales des Sc. Nat.' 4th ' series, Bot. tom. ix. cah. 5. CHAP. VI. CROSSED AND SELF-FERTILISED PLANTS. 189 this may be' attributed, at least in chief part, to the exclusion of moths. Six fLowers on a plant covered by a net were crossed with pollen from a distinct plant and produced six capsules, containing by we.ight 4 · 44 grains of seed. Six other fLowers were fertilised with their own pollen and produced only three capsules, containing only 1· 49 grains weight of seed. From this it follows that an equal number of crossed and self-fertilised capsules would have contained seeds by weight as 100 to 67. I should not have thought the proportional contents of so few capsules worth giving, had not nearly the same result been confirmed by several subsequent trials. Seeds of the two lots were placed on sand, and many of the self-fertilised seeds germinated before the crossed, and were rejected. Several pairs in an equal state of germination were planted on the opposite sides of Pots I. and II. ; but only the tallest plant on each side was measured. Seeds were also sowp. thickly on the two sides of a large pot (III.), the seedlings being afterwards thinned, so that an equal number was left on each side ; the three tallest on each side being measured. The pots were kept in the greenhouse, and the plants were trained up sticks. For some time the young crossed plants had no advantage in hejght over the self-fertilised; but their leaves were larger. When fully grown and in flower the plants were measured, as follows :- TABLE LXXVI. Petun~·a violacea (First Generation). No. of Pot. Crossed Plants. Self-fertilised Plants. Inches. Inches. I. 30 20~ II. 34~ 27~ III. 34 28~ 30~ 27 ~ 25 26 'Total in inches. 154 I 130 , The five tallest crossed plants here average 30 · 8, and the five tallest self-fertilised 26 inches in height, or as 100 to 84. |