THEORIES OF EMBRYOLOGY. 241 



from the anthers; and the finer it is, the more quickly it loses its 

 fecundating property. 



501. Theories of Embryology. So far as the application of the pollen 

 to the stigma is concerned, the process of fertilization can be easily 

 traced, but the changes which are subsequently produced on the pollen- 

 grain and the ovule are very obscure, require minute microscopic 

 research, and have led to numerous conflicting theories of Embryology. 

 It has been already stated, that some physiologists, especially Bernhardi, 

 believe, that in the case of Hemp, Lychnis dioica, and some other 

 plants, an embryo, or young plant, can be produced without the in- 

 fluence of the pollen. These views have not been confirmed. It has 

 been supposed that ha such plants as Hemp, where the stamens and 

 pistil are generally on separate individuals, there may occasionally occur 

 instances in which they are developed on the same plant. It is known 

 that this takes place in other cases. Thus, a specimen of Chamserops 

 humilis, or European Fan-palm, in the Botanic Garden of Edinburgh, 

 which had for upwards of twenty years shown pistilliferous flowers only, 

 exhibited, in 1847, both pistilKferous and staminiferous clusters,* and 

 produced perfect fruit without an artificial application of pollen. Again, 

 in Dioecious plants growing in the open air, the pollen may be carried 

 from other plants by the wind, and thus produce perfect seed. There 

 are thus numerous sources of fallacy in Bernhardi's observations ; and 

 Gartner's recent experiments seem to prove that Hemp is no exception 

 to the ordinary rule. Some, on the supposition of the correctness of 

 Bernhardi's views, have thought that the case might be analogous to that 

 of some Aphides, where one impregnation is sufficient to produce several 

 generations. Mr. Smith has recently stated, that a female plant of 

 Coelebogyne, belonging to the natural order of Euphorbiaccas, produced 

 perfect seeds in the garden at Kew, without any apparent contact of 

 pollen ; and Gasparrini maintains, that in the case of the cultivated 

 Fig, the seeds are the product of pistillate flowers only. Such cases, 

 if proved, will modify the views entertained relative to the action of 

 pollen. Can it be that, as in the case of some Cryptogamics, there are 

 in these anomalous cases two lands of cells present in the same organ, 

 some with fertilizing matter, and others containing the rudiments of 

 ovules, or of the embryo ? 



502. The subject of Embryology, or the development of the embryo 

 in the seed, has attracted much attention of late, and numerous opinions 

 have been advanced. There are many discrepancies as to the contents 

 of the ovule before impregnation ; some maintaining that the cavity of 

 the nucleus, or the embryo-sac alone, is developed before the pollen 

 is applied ; others, that besides it there is a utricle, or vesicle, in its 

 interior, which forms the first embryonic cell. The tubes in contact 



* It has clone so also in 1848. 

 R 



