Primula Sikkimensis (Scott) : 95 : 31.

Primula cortusoides (Scott) : 74 : 66.

Primula involucrata (Scott) : 72 : 48.

Primula farinosa (Scott) : 71 : 44.

Average of the nine species of Primula : 88.4 : 69.

Hottonia pal.u.s.tris (H. Muller) : - : 61.

Linum grandiflorum (the difference probably is much greater) : - : 69.

Linum perenne : - : 20.

Linum perenne (Hildebrand) : 0 : 0.

Pulmonaria officinalis (German stock, Hildebrand) : 0 : 0.

Pulmonaria angustifolia : 35 : 32.

Mitch.e.l.la repens : 20 : 47.

Borreria, Brazilian sp. : - : 0.

Polygonum f.a.gopyrum : - : 46.

Lythrum salicaria : 33 : 46.

Oxalis Valdiviana (Hildebrand) : 2 : 34.

Oxalis Regnelli : 0 : 0.

Oxalis speciosa : 15 : 49.

The two or three forms of the same heterostyled species do not differ from one another in general habit or foliage, as sometimes, though rarely, happens with the two s.e.xes of dioecious plants. Nor does the calyx differ, but the corolla sometimes differs slightly in shape, owing to the different position of the anthers. In Borreria the hairs within the tube of the corolla are differently situated in the long-styled and short-styled forms. In Pulmonaria there is a slight difference in the size of the corolla, and in Pontederia in its colour.

In the reproductive organs the differences are much greater and more important.

In the one form the stamens may be all of the same length, and in the other graduated in length, or alternately longer and shorter. The filaments may differ in colour and thickness, and are sometimes nearly thrice as long in the one form as in the other. They adhere also for very different proportional lengths to the corolla. The anthers sometimes differ much in size in the two forms. Owing to the rotation of the filaments, the anthers, when mature, dehisce towards the circ.u.mference of the flower in one form of Faramea, and towards the centre in the other form. The pollen-grains sometimes differ conspicuously in colour, and often to an extraordinary degree in diameter. They differ also somewhat in shape, and apparently in their contents, as they are unequally opaque. In the short-styled form of Faramea the pollen-grains are covered with sharp points, so as to cohere readily together or to an insect; whilst the smaller grains of the long-styled form are quite smooth.

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 pa.s.s 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 pal.u.s.tris (H. Muller) : 61.

Hottonia pal.u.s.tris (self) : 64.

Linum grandiflorum : 100.

Linum perenne (diameter variable) : 100 (?).

Linum flavum : 100.

Pulmonaria officinalis : 78.

Pulmonaria angustifolia : 91.

Polygonum f.a.gopyrum : 82.

Leucosmia Burnettiana : 99.

Aegiphila elata : 62.

Menyanthes trifoliata : 84.

Limnanthemum Indic.u.m : 100.

Villarsia (sp.?) : 75.

Forsythia suspensa : 94.

Cordia (sp.?) : 100.

Gilia pulch.e.l.la : 100.

Gilia micrantha : 81.

Sethia ac.u.minata : 83.

Erythroxylum (sp.?) : 93.

Cratoxylon formosum : 86.

Mitch.e.l.la repens, pollen-grains of the long-styled a little smaller.