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Show 248 CONCLUDING REMARKS CHAP. VI. seeds produced by the two or three forms often differ in number, and sometimes in size and weight; thus, five seeds from the long-styled form of Lythrum salicaria equal in weight six from the mid-styled and seven from the short-styled form. Lastly, short-stvled plants of Pulmonaria officinalis bear a larger nu~ber of flowers, and these set a larger proportional number of fruit, which however yield a lower average number of seed, than the long-styled plants. With heterostyled plants we thus see in how many and in what important characters the forms of the same undoubted species often differ from one another-characters which with ordinary plants would be amply sufficient to distinguish species of the same genus. As the pollen -grains of ordinary species belonging to the same genus generally resemble one another closely in all respects, it is worth while to show, in the following table (34), the difference in diameter between the grains from the two or three forms of the same heterostyled species in the forty-three cases in which this was ascertained. But it should be observed that some of the following measurements are only approximately accurate, as only a few grains .were measured. In several cases, also, the grains had been dried and were then soaked in water. Whenever they were of an elongated shape their longer diameters were measured. The grains from the short-styled plants are invariably larger than those from the longstyled, whenever there is any difference between them. The diameter of the former is represented in the table by the nu1nber 100. We here see that, with seven or eight exceptions out of the forty-three cases, the pollen-grains from one form are larger than thosefro m the other forn1 of the same species. The extreme difference is as 100 to 55; CHAP. VI. ON HETEROSTYLED PLANTS. 249 TABLE 34. Relative Diameter of the Pollen-gra'ins from the forms of the same Heterostyled Species ; those from the short-styled form being represented by_ 100. Dimorphic Species. From the Long-styled form. Primula veris • • 67 , vulgar is • • • 71 , Sinensis(Hildebrand) 57 , auricula . • . 71 Hottonia palustris (H. Muller) 61 , , (self) • 64 Linum grandiflorurn . • 100 , per.enne(diameterva-}100 (?) r1able). • • • · , flavum . • • • 100 Pulmonaria officinalis • • 78 , angustifolia • 91 Polygon urn fagopyrum. 82 Leucosmia Burnettiana 99 ..tEgiphila elata . • • • 62 Menyanthes trifoliata • 84 Limnanthemurn Indicum • 100 Villarsia (sp. ?) • . • 75 Forsythia suspensa • • 94 From the Longstyled form. Cordia (sp. ?) 100 Gilia pulchella • 100 , micraniha • • 81 Sethia acuminata • 83 Erythroxylum (sp. ?) • • 93 Cratoxy Ion formosum . • 86 Mitchella repens, pollen-grains of the long-styled a little smaller. Borreria ( sp. ?) . Faramea ( sp. ?) . . . • Suteria (sp. ?) (Fritz Muller) Houstonia ccerulea . • • 92 67 75 72 Oldenlanuia (sp. ?) . 78 Hedyotis (sp. ?) . • Coccocypselum (sp. ?) . . 88 Miiller) • • . Lipostoma (sp. ?) . Cinchona micrantha .(F.} 100 80 91 .Trimorphic. Species. Ratio expressing the extreme differences in diameter of the pollen-grains from the two sets of anthers in the three forms. Lythrum salicaria • , • . 60 Nesrea verticillata . • . . 65 Oxalis Valdiviana (Hildebrand) 71 , Regnelli . . 7 8 , speciosa • 69 , sensitiva • 84 Pontederia (sp. ?) . • 55 Ratio between the diameters of the pollengrains of the two sets of anthers in the same form. Oxalis rose~, long-sty led form} 83 (Hildebrand) . . . , compressa, short-styled l 83 form . . . . .1 Pontederia (sp. ?) short-styled} form. . . . 87 " other sp., mid-styled} 86 form. • . • and we should bear in mind that in the case of spheres differing to this degree in diameter, their contents differ in the ratio of six to one. With all the s~ecies in which the grains differ in diameter, there Is no exception to the rule that those from the |