With respect to the pistil, the style may be almost thrice as long in the one form as in the other. In Oxalis it sometimes differs in hairiness in the three forms. In Linum the pistils either diverge and pass out between the filaments, or stand nearly upright and parallel to them. The stigmas in the two forms often differ much in size and shape, and more especially in the length and thickness of their papillae; so that the surface may be rough or quite smooth. Owing to the rotation of the styles, the papillose surface of the stigma is turned outwards in one form of Linum perenne, and inwards in the other form. In flowers of the same age of Primula veris the ovules are larger in the long-styled than in the short-styled form. The 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-styled plants of Pulmonaria officinalis bear a larger number 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 Table 6.34, 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 long-styled, whenever there is any difference between them. The diameter of the former is represented in the table by the number 100. TABLE 6.34. Relative diameter of the pollen-grains from the forms of the same heterostyled species; those from the short-styled form being represented by 100. DIMORPHIC SPECIES. Column 1: Name of species. Column 2: From the long-styled form : relative diameter. Primula veris : 67. Primula vulgaris : 71. Primula Sinensis (Hildebrand) : 57. Primula auricula : 71. Hottonia palustris (H. Muller) : 61. Hottonia palustris (self) : 64. Linum grandiflorum : 100. Linum perenne (diameter variable) : 100 (?). Linum flavum : 100. Pulmonaria officinalis : 78. Pulmonaria angustifolia : 91. Polygonum fagopyrum : 82. Leucosmia Burnettiana : 99. Aegiphila elata : 62.