OF DIMORPHIC AND TRTMOBPHIC PLANTS. 409 



in their power of yielding seed, but have merely varied tempora- 

 rily in fertility, Nevertheless we may reject this conclusion as 

 far as the less fertile plants are concerned, — first, because none of 

 the plants in Class IV. attained their proper height, which shows 

 that they were in some manner affected ; and, secondly, because 

 many of the plants in Classes IV. & V, produced anthers which 

 were either contabescent or included small and shrivelled pollen- 

 grains. And as in these cases the male oi^ns were manifestly 

 deteriorated, it is by far the most probable conclusion that the 

 female organs were likewise affected, and that this was the cause 

 of the reduced number of seeds. 



With respect to the three short-styled and three long-styled 

 plants in the three latter classes, which yield too higb a per- 

 centage of seeds, the explanation is much more doubtful. The 

 normal standard for the long-styled form was deduced by counting 

 the seeds in twenty three capsules, and for the short-styled form 

 from twenty-five capsules. I do not pi*etend that this is a suffi- 

 cient number of capsules for absolute accuracy ; but my experience 

 leads me to believe that a very fair result would thus be gained. 

 As, however, the maximum number observed in the twenty-five 

 capsules of the short-styled form is low, the standard in this case 

 may possibly be not quite high enough. In the case of the illegi- 

 timate plants, in order to avoid overestimating their infertility, 

 ten very fine capsules were always selected ; and the years 18G5 

 and 1866, during which the plants in the three latter classes were 

 observed, were highly favourable for seed-production. JS'ow, if 

 this plan of selecting very fine capsules during favourable seasons 

 had been followed for obtaining tlie normal standards, insteiid of 

 taking, during various seasons, the first capsules which came to 

 hand, the standards would undoubtedly liave been considerably 

 higher; and thus the fact of the six foregoing plants appearing to 

 yield an unnaturally high percentage of seeds may, perhaps, be 

 accounted for. On this view, these plants are, in fact, merely 

 fully fertile, and not fertile to an abnormal degree. Nevertheless, 

 as characters of all kinds are liable to variation, especially witli 

 organisms unnaturally treated, and as in the three first and more 

 sterile classes, the plants derived from the same parents, and 

 treated in the same manner, certainly did vary much in sterility, it 

 is possible that certain plants, in the latter and more fertile classes, 

 may have varied so as to have acquired an abnormal degree of 

 fertility. But it should be especially observed that, if my stan- 

 dards err in being too low, the sterihty of all the many sterile 



I*INK, PBOC- — BOTANY, VOL. X. 2 E 



