I owe to the kindness of Fritz Muller dried flowers of this plant from St. Catharina, in Brazil. In the long-styled form the stigma stands in the mouth of the corolla, above the anthers, which latter are enclosed within the tube, but only a short way down. In the short-styled form the anthers are placed in the mouth 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 Rubiaceae. Nevertheless there is a considerable difference in the size of the pollen-grains 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 coerulea (Rubiaceae). Professor Asa Gray has been so kind as to send me an abstract of some observations made by Dr. Rothrock on this plant. The pistil is exserted in the one form and the stamens in the other, as has long been observed. The stigmas of the long-styled form are shorter, stouter, and far more hispid than in the other form. The stigmatic hairs or papillae on the former are .04 millimetres, and on the latter only .023 millimetres in length. In the short-styled form the anthers are larger, and the pollen-grains, when distended with water, are to those from the long-styled form as 100 to 72 in diameter. Selected capsules from 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. Professor Asa Gray informs me that the other North American species of this genus are likewise heterostyled. Oldenlandia [sp.?] (Rubiaceae).