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Show 118 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. length, those of the short-styled being rather the lop.gest; and the anthers of both are seated in the mouth of the corolla. Nor could I detect any difference in the size of the pollen-grains, when dry or after being soaked in water. The stigmas of the long-styled form stand clear above the anthers, and the whole pistil is longer than that of the short-styled, in about the ratio of 3 to 2. The stigmas of the short-styled form are seated beneath the anthers, and they are considerably shorter than those of the long-styled form. This latter difference is the most important one of any between the two forms. GILIA (IPOMOPSIS) PULOHELLA VEL AGGREGATA (POLEMONIAOElE). Professor Asa Gray remarks with respect to this plant: "the tendency to dimorphism, of which there are traces, or perhaps rather incipient manifestations in various portions of the genus, is most marked in G. aqgregata.''* He sent me some dried flowers, and I procured others from Kew. They differ greatly in size, some being nearly twice as long as others (viz. as 30 to 17), so that it was not possible to compare, except by calculation, the absolute length of the organs from different plants. Moreover, the relative position of the stigmas and anthers is variable: in some long-styled flowers the stigmas and anthers were exserted only just beyond the throat of the corolla; whilst in others they were exserted as much as -{:0 of an inch. I suspect also that the pistil goes on growing for some time after the anthers have dehisced. Nevertheless it is possible to class the flowers under two forms. In some of the long-styled, the length of pistil to that of the short-styled was as 100 to 82; but this result was gained by reducing the size of the corollas to the same scale. In another pair of flowers the difference in length between the pistils of the two forms was certainly greater, but they were not actually measured. In the short-sty led flowers whether large or small, the stigma is seated low down within the tube of the corolla. The papillre on the long-styled stigma are longer than those on the short-styled, in the ratio of 100 to 40. The filaments in some of the short-styled flowers were, to those of the long-styled, as 100 to 25 in length, the free, . or * 'Proc. American Acad. of Arts and Sciences,' June 14, 1870, p. 275. CHAP. III. PHLOX SUBULATA. 119 unattached portion being alone measured; but this ratio cannot be trusted, owing to the gre.at variability of the stamens. The mean diameter of eleven pollen-grains from long-styled flowers, and of twelve from the short-styled, was exactly the same. It follows from these several statements, that the difference in length and state of surface of the stigmas in the flowers is the sole reliable evidence that this species is heterostyled; for it would ·be rash to trust to the difference in the length of the pistils, seeing how variable they arc. I should have left the case altogether doubtful, had it not been for the observations on the following species; and these leave little doubt on my mind that the present plant is truly heterostyled. Professor Gray informs me that in another species, G. coronopifolia, belonging to the same section of the genus, he can see no sign of dimorphism. GrLIA (LEPTOSIPHON) MICRANTHA. A few flowers sent me from Kew had been somewhat injured, so that I cannot say anything positively with respect to the position and relative length of the organs in the two form~. But their stigmas differed almost exactly in the same manner as in the last species ; the pa pillre on the long-sty led stigma being longer than those on the short-styled, in the ratio of 100 to 42. My son measured nine pollen-grains from the long-styled, and the same number from the short-styled form; and the mean diameter of the former was to that of the latter as 100 to 81. Considering this diffe~ence, as well as that between the stigmas of the two forms, there can be no doubt that this species is heterostyled. So probably is Gilia nudicaulis, which likewise belongs to the Leptosiphon section of the genus, for I hear from Professor .Asa Gray that in some individuals the style is very long, with the stigma more or less exserted, whilst in others it is deeply included within the tube; the anthers being always seated in the throat of the corolla. PHLOX SUBULATA (POLEMONIAOElE). Professor Asa Gray informs me that the greater number of the species in this genus have a long pistil, with the stigma more or less exserted; whilst several other species, especially the annuals, have a short pistil seated low down within the tube of the corolla. In all the species the anthers are arranged one |