173 >[R. C. DARWIN O:^ THE SEXtlAI. r.ET.ATIOyS OF 



croseoxje, and I found I could always (with one exception) distin- 

 guisli them : I then showed the specimens to two other persons, 

 and they likewise distinguished the two kinds and pointed out 

 which was the largest. The capsules of this form contain, on an 

 average, 93 seeds : how this average was obtained will presently 

 be explained. I repeatedly observed that the seed, when cleaned, 

 seemed larger than that from the mid-styled or short-styled 

 forms ; consequently I placed 100 loug-stylod seeds in a good 

 balance, and by the double method of weighing found that they 

 equalled 121 seeds of the mid-styled and 142 of the short-styled ; 

 or, in short, that five long-styled seeds equalled six mid-styled and 

 seven short-styled seeds. These slight diiferences in the weight of 

 the seed, and, as we shall soon see, in the average number produced, 

 are worth recording, as they characterize not mere varieties but 

 coexisting forms of the same species. 



3Iid-styled form. — The pistil occupies the position represented 

 in the diagram, with its extremity considerably, but in a variable 

 degree, upturned ; the stigma is seated between the anthers of 

 the long and the short stamens. The six longer stamens correspond 

 in length with the pistil of the long-styled form ; their filaments 

 are coloured bright pink ; the anthers are dark-coloured, but 

 from containing bright green pollen and from their early de- 

 hiscence they appear emerald-green. Hence the general appear- 

 ance of these stamens is remai'kably dissimilar from that of the 

 longer stamens of the long-styled form. The six shorter stamens, 

 enclosed within the calyx, resemble in all respects the shorter 

 stamens of the long-styled form, and both correspond in length 

 with the short pistil of the short-styled form. The green pollen- 

 grains of the longer stamens are plainly larger than the yellow 

 pollen-grains of the shorter anthers : this fact was conspicuous in 

 several camera-lucida drawings made for me by my sou, Mr. W. E. 

 Danvin. There is some variability in size, but y-J-J^ of an inch 

 may be taken as about the average diameter of the green pollen- 

 grains when distended mth water, and y-^ij aa the diameter of 

 the yellow grains of the shorter stamens ; so that the difi'ercnce 

 in diameter is in about the proportion of four to three. The cap- 

 sules contain, on an average, 132 seeds ; but, perhaps, as we shall 

 see, this is rather too high an average. The seeds themselves are 

 smaller than those of the long-styled form. 



Short-styled form. — The pistil is here very short, not one-third 

 of the length of that of the long-styled form. It is enclosed 

 within the calyx, which, differently from in the other two forms. 



