SEED DIVISION. 51 



oablc of i)reserviug' ])olleu as is the seed-vessel of the fern of retainiDg 

 he vitality of the seed — a fact that no one now questions." 



Papilionaceous tiowers — those of plants of the leguminous order, as 



iic pea, so called from the butterfly-shape of their tiowers — offer innu- 



crable adaptations for cross-fertilization. "The stamens of the Pos- 



itieria fragrans (one of the Eubiaceie)," says Fritz MuUer, in the Botan- 



•iclio Zeitioiri, "are irritable, so that as soon as a moth visits a flower the 



anthers explode and cover the insect with pollen. One of the filaments, 



which is broader than the others, then moves and closes the flower for 



about twelve hours, after which time it resumes its original position. 



Thus the stigma cannot be fertilized by pollen from the same flower, 



but only by that brought by a moth from some other flower. Endless 



other beautiful contrivances for this purpose could be specified." 



CROSS AMD SRLF FKinMIJTiATlON OS" PLANTS, 



In the compilation of facts relative to the effects of cross and self 

 fertilization of plants, so far as it relates to seed production, I am largely 

 indebted to the latest work of Charles Darwin upon the subject. His 

 investigations have done much toward the solution of niany of the most 

 l)uzzliug questions relating to interbreeding and self-fertilization. He 

 has shown most conclusive!}' that plants bearing hermaphrodite floAvers 

 can be interbred mor<^^. closelj' than is possible with bisexual annuals, 

 and arc tlierefore well lUted to throw light on the nature and extent of 

 the good eiiects of crossing and on the evil effects of close interbreeding 

 and self-fertilization. Or, in other words, " a crossed plant, seedling, or 

 seed means one of crossed parentage ; that is, one derived from a flower 

 fertilized with pollen from a distinct plant of the same species ; and 

 that a self fertilized plant, seedling, or seed means one of self^fertilized 

 parentage ; that is, one derived from a flower fertilized with pollen from 

 the same flower, or sometimes, when thus stated, from another flowei- 

 on the same jilaut." 



The conclusion arrived at through the most careful and painstaking" 

 observations, extending over a period of many years, is that cross-fertili- 

 zation is generally beneficial and self-fertilization injurious. This, in 

 the experiments referred to, was shown, not only by the "difference in 

 height, weight, constitutional vigor, and fertility of the offspring from 

 crossed and self-fertilized flowers, but also in the number of seeds pro- 

 duced by the parent plants. This cannot be attributed to the superiority 

 of the crossed, but to the inferiority of the self-fertilized seedlings, due to 

 the iiijnrious effects of self fertilization." " "Whether the evil from self- 

 fertilization goes on increasing during successive generations is not as 

 yet known, but we may infer from my experiments that the increase, 

 if any, is far from rapid. After plants have been propagated by self- 

 fertilization for several generations, a single cross with a fresh stock 

 restores their in'istine vigor, and we have a strictly aualagous result 

 with our domestic animals. The good results of cross-fertilization are 

 triiiismitted by plants to the next generation, and, judging from the 

 vMiieties of the common pea, to many succeediug generations. But 

 this may merely be that crossed plants of the first generation are ex- 

 tremely vigorous, and transmit their vigor, like any other character, to 

 then- successors." 



Darwin claims with characteristic positiveness that the "advantages 

 of cross-fertilization do not follow from some mysterious virtue in the 

 mere union of two distinct individuals, but from such individuals having 

 been subjected during i^revious generations to different conditions or to 



