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Show CHAP. II. IPOMCEA PURPUREA. 58 ·e pro d uc t'I v e than the self-always in some degree morer standard they are com-fertilised plants, by w~atev ·eatly ; but this depends ·ed The degree differs gr t lren of the seeds pM . aeW~ a~ . ch I. ef ly on whether l:ln averab f' both combined. 1 1 ne or o . alone, or of the c~ps_u es fat~ ~rossed plants is chiefly The relative supen~nty o ~ -reater number of capdue to their producing a roue lg containing a larger sules, and not to eac h capFsour ei nstance, in the t h"u d average number of seeds. d If-fertilised plants pro-generation the crossed an_ sef 100 to 38 whilst the duced capsules. I·D the ratioh o ·ossed pla'n ts were to seeds in the capsu 1e s . o. n t el acnrt s only as 100 to n4 u . those on the self-fertilised P les on two sclf-t" n the capsu - In the eighth genera I? 1 d d in the above table), 1 t. ( ot Inc u e fertilised p an s n d thus not subjected to any grown in separ_ate pots an lar e average of 5 ·1 seed~. competition, yielded the s!Jes roduced by the si~i. The smaller number of c~p ·t p but not altogether,, fertilised plants may be Idn par 'r hei"ght. this being h · 1 e SIZe 0 ' attributed to t en. essen ed constitutional vigour, so chiefly due to then lessen te with the crossed ~ t ble to compe d that they were no a t The seeds produce plants growing in the samet~o :rossed plants were not by the cross~d flowers ~n se~f-fertilised seeds on the always ~~aVler t~~: tT:e lighter seeds, whether pro· self-fertilised pla . . If-fertilised flow ers, generally duced from crossed or se . d I may add that b .(! th heavier see s. G d germinated elore ~ . few exceptions, fiowere the crossed plants, w~t~ very t as might have before their self-fertilised opponhe~ sh, t and vigour. d f th · · greater eig been e~pect~. ;~~t·l-:yu of the self-fertilised plants :vas The Impaue er l I 1 b their anthers being shown in another way, name y, y th crossed plants. smaller than tl1ose in th~ flohwers on the generation, but This was first observed In t e seven CnAr. n. SUMMARY OF OBSERVATIONS. 59 may have occurred earlier. Several anthers from flowers on the crossed and self-fertilised plants of the eighth generation were compared under the microscope ; and those from the former were generally longer and plainly broader than the anthers of th self-fertilised plants. The quantity of pollen contained in one of the latter was, as far as could be ju<lged by the eye, about half of that contained in one from a crossed plant. The impaired fertility of the self-fertilised plants of the eighth generation was also shown in another manner, which may often be observed in hybrids-namely, by tho :first-fonned flowers being sterile. For instance, tho :fifteen :first flowers on a self-fertilised plant of one of tho later generations were carefully fertilised with thoir own pollen, and eight of them dropped off; at the same time :fifteen flowers on a crossed plant growing in the same pot were self-fertilised, ancl only one dropped off. On two other crossed plants of the same generation; several of the earliest flowers were observed to fertilise thmnselves and to produce capsules. In the plants of the ninth, and I believe of some previous generations, very many of the flowers, as already stated, were slightly monstrous ; and this probably was connected with their lessened fertility. All the self-fertilised plants of the seventh generation, and I believe of one or two previous generations, produced flowers of exactly the same tint, namely, of a rich dark purple. So did all the plants, without any exception, in the three succeeding generations of selffertilised plants; and very many were raised on account of other experiments in progress not here recorded. My attention was :first called to this fact by 1ny gardener re1narking that there was no occasion to label the self-fertilised plants, as they could always be known by their colour. The flowers were as uniform in tint |