FERTILIZATION IN THE VEGETABLE KINGDOM. 231 



blossoms nearest within reach, greatly favors such intercross- 

 ing. So does the remarkable number of flowers which bees 

 are able to visit in a short time (of which mention wdll be 

 made), and the fact that they are unable to perceive with- 

 out entering a flower whether other bees have exhausted the 

 nectar. Then dichogamy (the maturation of one sex in a 

 I hermaphrodite flower earlier than the other) is so prevalent 



that it may almost be regarded as the rule ; and this ensures 

 such crossing between few-flowered plants, and greatly favors 

 it in the case of spikes, racemes, and the like. For, proteran- 

 dry being the commonest arrangement, so that the younger 

 flowers act as male, and the older as female, the bees habitu- 

 ally alighting at the bottom and proceeding upward, they 

 carry the pollen from the upper and younger flowers to stig- 

 mas of the lower and older flowers of the next spike, and so 

 on. Heterogonism, which is less common, operates precisely 

 like complete dioecious separation of the sexes in this respect, 

 and with the advantage that all the individuals are seed-bear- 

 ing. Most of the special arrangements peculiar to certain 

 families, such as Orchids, — or to plants, such as Posoqueria, 

 with its wondrous mechanism for quickly stopping out access 

 to the stigma when the pollen is violently discharged upon 

 some insect, but opening the orifice the next day, — are of a 

 kind to favor the crossing of distinct plants. Prepotency of 

 other pollen, which may accompany the other arrangements 

 or exist independently, acts largely and powerfully toward 

 the same end. Our author investigates this at some length : 

 we cite for illustration a single but strong case. The stig- 

 mas of a long-styled Cowslip were supplied with pollen from 

 the same plant, and again after twenty-four hours, with pol- 

 len of a short-styled, dark-red Polyanthus, a variety of the 

 same species : from the resulting seeds tw^enty seedlings were 

 raised, and all of them bore reddish flowers ; so that the 

 effect of the plant's own pollen, though placed on the stigmas 

 twenty-four hours previously, was destroyed by that of the 

 red variety. The same thing is shown by the impossibility 

 in many cases of raising two varieties of the same species 

 pure if they grow near each other. " No one who has had any 



