IN SEVERAL SPECIES OF THE GENUS LINUM. 75 



apparently never penetrate the stigmatic tissue deeply, and the 

 stigmas themselves do not become discoloured and twisted. 



This seems to me a remarkable physiological fact. The pollen- 

 grains of the two forms are undistinguishable under the micro- 

 scope ; the stigmas dift'er only in length, degree of divergence, and 

 in the size, shade of colour, and approximation of their papilte, these 

 latter differences being variable and apparently simply due to the 

 elongation of the stigma. Yet we plainly see that the two pollens 

 and the two stigmas are widely dissimilar in action — the stigmas of 

 each form being almost powerless on their own pollen, but causing, 

 through some mysterious influence, by simple contact (for I could 

 detect no viscid secretion), the pollen-grains of the opposite fonn 

 to protrude their tubes. It may be said that the two pollens and 

 the two stigmas by some means mutually recognize each other. 

 Taking fertility as the criterion of distinctness, it is no exaggera- 

 tion to say that the poUen of the long-styled Linum grandiflorum 

 (and conversely of the other form) has been diilerentiated, with 

 respect to the stigmas of all the flowers of the same form, to a 

 degree corresponding with that of distinct species of the same 

 genus, or even of species of distinct genera. 



Linum perenne. — The dimorphism is here more conspicuous, and 

 has been noticed by several authors. In the long-styled form the 

 pistil is nearly twice as long as in short-styled ; in the latter the 

 stigmas are smaller and, diverging more, pass out between the fila- 

 ments of the stamens. I could detect no difierence in the size of 

 the stigmatic papillae ; in the long-styled form alone the stigmatic 

 surfaces turn round so as to face the circumference of the flower : 

 but to this point we shall presently return. Difterently from what 

 occurs in L. grandiflorum, the long-styled flowers have stamens 

 hardly more than half the length of those of the short-styled. The 

 size of the pollen-grains is rather variable ; after some doubt, I have 

 come to the conclusion that there is no uniform difierence between 

 the pollen of the two forms. The long stamens in the short-styled 

 form project to some height above the corolla, and, apparently from 

 exposure to the light, the filaments are coloured blue. These longer 

 stamens correspond in height with the lower part of the stigmas 

 of the long-styled flowers ; and the shorter stamens of the latter 

 form correspond in the same manner in height with the shorter 

 stigmas of the short-styled flowers. 



I raised from seed twenty-six plants, wliich proved to be twelve 

 long-styled and fourteen short-styled. They flowered well, but 

 were not large plants. As I did not expect them to flower so 



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