120 HETEROSTYLED DIMORPHIC PLANTS. Chap. III. 



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 (Polemoniace^e). 



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 an- 

 thers are arranged one below the other, the uppermost just 

 protruding from the throat of the corolla. In Phlox subu- 

 lata alone he has " seen both long and short styles ; and 

 here the short-styled plant has (irrespective of this char- 

 acter) been described as a distinct species (P. nivalis, P. 

 Hentzii), and is apt to have a pair of ovules in each cell, 

 while the long-styled P. subulata rarely shows more than 

 one." * Some dried flowers of both forms were sent me by 

 him, and I received others from Kew, but I have failed 

 to make out whether the species is heterostyled. In two 

 flowers of nearly equal size, the pistil of the long-styled 

 form was twice as long as that of the short-styled; but in 

 other cases the difference was not nearly so great. The 

 stigma of the long-styled pistil stands nearly in the throat 

 of the corolla; whilst in the short-styled it is placed low 

 down — sometimes very low down in the tube, for it varies 

 greatly in position. The stigma is more papillose, and of 

 greater length (in one instance in the ratio of 100 to 67), 

 in the short-styled flowers than in the long-styled. My son 

 measured twenty pollen-grains from a short-styled flower, 

 and nine from a long-styled, and the former were in diam- 

 eter to the latter as 100 to 93; and this difference accords 

 with the belief that the plant is heterostyled. But the 

 grains from the short-styled varied much in diameter. He 

 afterwards measured ten grains from a distinct long-styled 

 flower, and ten from another plant of the same form, and 

 these grains differed in diameter in the ratio of 100 to 90. 

 The mean diameter of these two lots of twenty grains was 

 to that of twelve grains from another short-styled flower 



* ' Proc. American Acad, of Arts and Sciences/ June 14, 1870, p. 248. 



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