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Show 132 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. which latter are enclosed within the tube, but only a short way down. In the short-styled form the anthers are placed in the 1nouth of the corolla above the stigma, which occupies the same position as the anthers in the other form, being seated only a short way down the tube. Therefore the pistil of the long-styled form does not exceed in length that of the short-styled in nearly so great a degree as in many other Rubiacem. Nevertheless there is a considerable difference in the size of the pollengra, ins in the two forms; for, as Fritz Muller informs me, those of the short-styled are to those of the long-styled as 100 to 75 in diameter. HoUSTONIA CCERULEA (RUBIACElE). Prof. Asa Gray has been so kind as to send me an abstract of f;Omo observations made by Dr. Rothrock on this pbnt. The pi. til is exserted in the one form and the stmnens in the other, as has long been observed. The stigmas of the longstyled form are shorter, stouter, and far more hispid than in the other form. The stigmatic hairs or papillm on the former a,rc · 04 mm., and on the latter only · 023 mm. in length. In tho short-styled form the anthers are larger, and the pollen-grains, when distended with water, are to those from the long-styled forn1 as 100 to 72 in diameter. Selected capsules frmn some long-styled plants growing in the Botanic Gardens at Cambridge, U.S., near where plants of the other form grew, contained on an average 13 seeds; but these plants must have been subjected to unfavourable conditions, for some long-styled plants in a state of nature yielded an average of 21· 5 seeds per capsule. Some short-styled plants, which had been planted by themselves in the Botanic Gardens, where it was not likely that they would have been visited by insects that had previously visited long-styled plants, produced capsules, eleven of which were wholly sterile, but one contained 4, and another 8 seeds. So that the short-styled form seems to be very sterile with its own pollen. Prof. Asa Gray informs me that the other North A1nerican species of this genus are likewise heterostyled. 0LDENLANDIA [SP. ?] (RUBIACElE). Mr. J. Scott sent me from India dried flowers of a heterostyled species of this genus, which is closely allied to the last. CHAP. III. RUBIACEJE. 10•) v0 The pistil in the long-styled flowers is longer by about a qua,rter of its length, and the stamens shorter in about the same proportion, than the corresponding organs in tho short-. tylcd flowers. In the latter the anthers are longer, and the divergent stigmas decidedly longer and apparently thinner than in the long-styled form. Owing to the state of the specimens, I could not decide whether the stigmatic papillre were longer in the one form than in the other. The pollen-grains, distended with water, from the short-styled flowers were to those from the longstyled as 100 to 78 in diameter, as deduced frmn the mean of ten measurements of each kind. HEDYOTIS [SP. ?] (RUBIACElE). Fritz Muller sent me from St. Catharina, in Brazil, chied flowers of a small delicate species, which grows on wet sand near the edges of fresh-water pools. In the long-styled form the stigma projects above the corolla, and stands on a level with the projecting anthers of the short-styled form; but in the latter the stigmas stand rather beneath the level of tho anthers in the other or long-styled form, these being enclosed within the tube of the corolla. The pistil of the long-styled form is nearly thrice as long as that of the short-styled, or, speaking . trictly, as 100 to 39; and the papillre on the stigma of the former arc broader, in the ratio of 4 to 3, but whether longer than those of the short-styled, I could not decide. In the short-styled form, the anthers are rather larger, and the pollen-grains are to those from the long-styled flowers, as 100 to 88 in diameter. Fritz Muller sent me a second, small-sized species, which is likewise heterosty led. CoccocYPSELUM [sP. ?] (RuBIACElE). Fritz Muller also sent me dried flowers of this plant from St. Catharina, in Brazil. The exscrted stigma of the long-styled form stands a little above the level of the exsertecl anthers of the short-styled fol'ln; and the enclosed stigma of the latter also stands a little above the level of the enclosed anthers in the Jongstyled form. The pistil of the long-styled is about twice as long as that of the short-styled, with its two stigmas consi lcrably longer, more divergent, and more curled. F1·itz Muller informs |