10 



ON HYBRIDIZATION AMONGST VEGETABLES. 



tinued to vivify the embryo at a later period, since it can elude 

 the microscopic research of Mr. Brown in a seed so large as that 

 of Ilymenocallis. I have cut open seeds of Hymenocallis an inch 

 and a half long, and found no visible embryo, but a large cavity ; 

 yet the rest of them, being left in the damp ground, acquired 

 visible embryos, and sprouted some months after. If, therefore, 

 as I apprehend, the pollen tubes cannot reach the ovules without 

 deriving substance from the cognate juices of the style through 

 which they descend, it becomes easy to understand how there 

 may be sufficient affinity between them to carry on the process to 

 the degree necessary for quickening the capsule, but not to carry 

 it on to the point requisite, and with the excitement and irrita- 

 bility necessary for reaching the ovule, and stimulating it to open 

 its aperture for the reception of the substance conveyed by the tube 

 from the interior of the grain of pollen. It is also easy to under- 

 stand how moisture, either to feed the plant inwardly, and make 

 its juices abundant, or to affect the stigma outwardly, may be 

 necessary to the fertilization of the ovules. If a chemist could 

 analyze the pollen before application, and the tubes after, perhaps 

 it would appear that the pollen is deficient, and, in order to be 

 available, must be deficient in some one of the ingredients which 

 will be found in the tubes. If it be true, as I imagine, that it is 

 necessary for the pollen to derive from the style some chemical ad- 

 junct to increase its bulk, and to enable it to irritate the aperture 

 of the ovule and obtain access, it will become manifest why it is, 

 that in some genera intermixed produce is easily obtained — in 

 others not ; because it depends upon the close similarity of con- 

 stitution and chemical relation of the component parts of the two 

 plants. We can easily understand that the individual which, on a 

 hot and barren soil, dwindled, after the dispersion by the deluge, 

 to a slender annual, may have acquired such different chemical 

 qualities, that it has not now sufficient affinity to the species which 

 in a moist and luxuriant position has become the master of a forest, 

 twining its colossal arms round the loftiest of its inhabitants ; while 

 two other species, though very different in some striking points of 

 conformation, may have such constitutional similarity, and such 

 identity of component ingredients, as to have precisely the same 

 chemical affinities and intermix readily. Why is it that in the 

 genus Hippeastrum all the several natural species, forms, or 

 varieties of that plant (I care not by what title their variation is 

 styled) breed more readily by the pollen of any other, however 

 complicated by cross-breed, than by its own ; and that in the 

 genus Habranthus, most closely allied to it, every attempt to 

 cross the several natural sorts has as yet entirely failed ? The 

 facts are so. Why is it that in the genus Zephyranthes, closely 

 akin to Habranthus, and making seed freely, crosses are obtained 



