1846.] Fertilization of Plants. 57 



bryo sac. It pushes before it this part of the sac, which, in yield- 

 ing to the pressure forms a cavity in which the extremity of the 

 tube is buried. The part of the pollen tube buried in the embryo 

 sac passes successively through all the degrees of organization to 

 that which constitutes the embryo." 



This is the outline of the German theory, given in the words of 

 its founder, as nearly as a translation can do it. It will be seen 

 that by this theory the stamen is alone the organ of reproduction, 

 and the pistil only acts as a kind of nurse to protect and nourish 

 the embryo committed to its care. Endleicher modifies the above, 

 by supposing the fluid substance of the stigma to fecundate the 

 pollen and make the pollen tubes penetrate to the ovary, linger 

 thinks the pollen grains are fecundated before their emission from 

 the anthers. 



In France, England, and the United States, these views have 

 been but badly received, and we believe the Linneean notions of 

 fecundation almost universally prevail out of the German states. 

 It would be impossible to give within any moderate limits the 

 reasons for these various opinions, and considering the purposes 

 for w^hich this article w^as written, not desirable. 



Whichever theory we may adopt, w^e should not be led to infer 

 that the quantity of pollen could- exert any influence over fecun- 

 dation; that is, we do not see why one pollen tube might not as 

 effectually impregnate one ovule as though all the neighboring 

 ones were subjected to the same influence. But this does not 

 seem to be the case in some plants, at least. Koelreuter says that 

 fifty to sixty grains of pollen are necessary to fecundate the thirty 

 grains of the hibiscus trioneus, and that no fewer will do it. Gaert- 

 ner has made experiments on this subject, which seem to lead to 

 the same result. He experimented on the malva Tuauritiana, the 

 purple, ivy-leaved mallows, of the gardens. There are ten stig- 

 mas, and a single grain of pollen on each produced no eifect. 

 The flower fell off" without any impregnation. Two grains on 

 each stigma, or twenty to each flower, produced no effect. Thirty 

 seemed to stimulate the organs, as the calyx remained on, persist- 

 ent, but no grains or seeds were produced. Forty to each flower 



