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Show 362 PLANTS STERILE WITHOUT INSEO'r-AID. CIIAP. :X .. this was a false appearance; 60 heJds on the latter yielded 349 grains weight of seeds, whereas GO on the covered-up plants yielded only 63 grains, and many of the seeds in tbo latter lot were poor and aborted. Therefore the fiowol'R which were visited by bees produced between five and ~ix times as many seeds as those which were protected. Tbo covered-up plants not having been much exhausted by seedbearing, bore a second considerable crop of flower-stem. ·, whilst the exposed 'plants did not do so. Gytisus laburnum (Leguminosre ).-Seven flower-racemes ready to expand were enclosed jn a large bag made of net, and they did not seem in the least injured by this treatment. Only three of tbem produced any pods, each a single one ; rtnd these three pods contained one, four, and five seeds. So that only a single pod from the seven racemes included a fair complement of seeds. Cuphea p11.rp1J.rea (Lythracere).-Produced no seeds. Other flowers on the same plant artificially fertilised under the net yielded seeds. Vinca maJor (Apocynacere).-ls generally quite , torile, but sometimes sets seeds when artificially cross-fertilised : see my notice, 'Gardeners' Chronicle,' 1861, p. 552. V. rosea.-Behaves in the same manner as the last species: 'Gardeners' Chronicle,' 1861, pp. 699, 736, 831. Taberncemontana echinata (Apocynacere).-Quite sterile. { Petunia violacea (Solanacere).-Quite sterile, as far as I have observed. l Solanum tuberosum (Solanacem).-Tinzmann says (' Gardcne~s' Chronicle,' 1846, p. 183) that some varieties arc quite stenlc unless fertilised by pollen from another vaTicty. . Primula scol'ica (Primulacere).-A non-J.imorphic species, ,~]uc~t is fertile with its own pollen, but is extremely stcnlc 1: insects are excluded. J. Scott, in' Journal Linn. Soc. Bot. vol. viii. 1864, p. 119. Cortusa matthioli (Primulacere).-Protccted plants com~let~ly sterile; artificially self-fertilised. flowers perfectly fertile. J. Scott, ibid. p. 84. 1 Cyclamen persicum (Primulace~).-During one season severa covered-up plants did not pToduce a single seed. Borago officinal is (Boraginacem ).-Protected plants produced about half as many seeds as the unprotected. Salvia tenori (Labiatre).-Quite sterile; but two or three flowers CHAP. X. PLANTS STERILE WITHOUT INSECT-AID. 363 on the summits ?f three of the spikes, which touched the net. ~hen the wmd blew, produced a few seeds. This ster:l:ty was not due to .the injul'ious effects of the net, for I fertilised five :B.owers With pollen from an adjoining plant, and tJ:ese all ywlded. fine seeds. I removed the net, whilst one httJe branch still bore a few not completely faded flo':ers, a~d these were visited by bees and yielded seeds. S. cocc~:"ea.-~ome cov~red-up pJants produced a good many fruits, but not, I think, half as many as did the uncovered plants; twenty-eight of the fruits spontaneously .produced by the pr?tected plant contained on an average only 1·45 seeds, whilst some artificially self-fertilised fruits on the same plant contained niore than twice as many, viz. 3 · 3 seeds. . ' Bignonia (unnamed species) (Bignoniacere).-Quite sterile: see my account of self-sterile plants. JJigitu.l'l's purpurert (Scrophulariacere).-Extremely sterile only a few poor capsules being produced. ' Lz'naria vulgaris (Scrophulariacere).-Extremely sterile. .Anti·rrhinum rnajus, red var. (Scrophulariacere).-Fifty pods ga~hered from a large plant under a net contained 9 · 8 grains wmgh~ of seeds; bu~ many (unfortunately not counted) of the fifty pods contamed no seeds. Fifty pods on a plant fully exposed to the visits of humble-bees contained ~3 ·1 grains weight of seed, that is, more than twice tbe weio·ht · but in this case again, several of the fifty pods contained n~ seeds. A. m~ius (white var., with a pink mouth to the corolla).Fifty pods, of which only a very few were empty, on a covered-up plant contained 20 grains wejght of seed· so that this variety seems to be much more self-fertile than the . previous one. \Vith Dr. W. Ogle ('Pop. Science Review,' Jan. ] t->70, p. 52) a plant of this species was much more sterile when protected from insects than with me for it produced only two small capsules. As showing' the efficiency of bees, I may add that Mr. Crocker castrated some young flowers and left them uncovered; and these pi'oduced as many seeds as the unmutilated flowers . .A. mafus (peloric var.).-'l'his variety is quite fertile when artificially fertilised with its own pollen, but is utterly sterile when left to itself and uncovered, as humble-bees cannot crawl into the narrow tubular flowers. |