io8 



HYBRIDISING AND CROSS-BREEDING. 



Umbelliferae and many species of Cruciferae and Saxifraga. 

 Finally, Kerner draws the conclusion that those plants whose 

 coherent pollen renders insect agency necessary for their fer- 

 tilisation can only have existed in very recent geological 

 periods; and those new species or varieties must necessarily 

 have the advantage, and tend to become perpetuated, which 

 possess superior advantages, in respect to the climate in which 



Pollen-grain of Fumitory (Fumaria 

 officinalis, L), showing four of the 

 great pores on it (mag. 200 times). 



Pollen-grain of Chicory (C ichor inm In- 

 tybus) seen on two different sides (mag. 

 200 times). 



they grow, for the protection of their pollen from all injurious 

 influences. The plants, the remains of which are found in 'the 

 oldest geological formations, are generally of that class which 

 do not require insect agency for their fertilisation. 



Practically, it is often highly necessary to preserve pollen 

 from early-blooming plants with which to fertilise later-bloom- 



Pollen of the Tiger Lily (Lilinm tigrinum, 

 Ga wl. ) with a " slit. " A, Viewed in front ; 



B, Viewed at 

 times}. 



jne extremity (mag. 200 



A pollen- grain of Pelargonium 

 zonale, W., viewed in tivo different as- 

 pects to show its form. A, Side view, 

 B, Its extremity (mag. 200 times.) 



ing species or varieties, or vice versa, as the case may be. In 

 the case of some dioecious plants, which do not flower simul- 

 taneously, this is absolutely necessary, the common Aucuba 

 being a familiar example. By forcing late-blooming species 

 and forms, and by retarding earlier ones, we may succeed in 

 obtaining pollen at the precise moment when it is required ; 

 but it is a most important fact for all hybridisers to knqw, that 



