132 HETEEOSTYLED 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 

 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 Rubiacese. Never- 

 theless there is a considerable difference in the size of the pollen- 

 grains in the two forms; for, as Fritz Miiller informs me, those 

 of the short-styled are to those of the long-styled as 100 to 

 75 in diameter. 



HoirSTONIA OCBBULEA (RUBIAOEai). 



Prof. Asa Gray has been so kind as to send me an abstract of 

 some observations made by Dr. Eothrock 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 papillee on the former 

 are '04 mm., and on the latter only "023 mm. in length. In the 

 short-styled form the anthers are larger, and the poUen-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. Prof. Asa 

 Gray informs me that the other North American species of this 

 genus are likewise heterostyled. 



OlDBNLANDIA [SP. ?] (EtJBIACE^). 



Mr. J. Scott sent me from India dried flowers of a hetero- 

 yled species of this genus, which is closely aUied to the last. 



