HYBRIDISING AND CROSS-BREEDING. 131 



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 

 irritability 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 understand how moisture, either to feed the plant in- 

 wardly and make its juices abundant, or to affect the stigma 

 outwardly, may be necessary to the fertilisation of the ovules, 

 If a chemist could analyse the pollen before application, and 

 the tubes after, perhaps it would appear that the pollen is de- 

 ficient, 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 adjunct 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 constitution 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 such sufficient affinity to the 

 species which in a moist and luxuriant position has become a 

 master of a forest, twining its colossal arms round the loftiest 

 of its inhabitants ; while two other species, though very differ- 

 ent in some striking points of conformation, may have such 

 constitutional similarity, and such identity of component in- 

 gredients, 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 Zephyranthus, closely akin to Hab- 

 ranthus, and making seed freely, crosses are obtained with 

 much difficulty, and, when obtained, are -rather disposed to 



