BOTANICAX SUBJECTS. 301 



can be distmguished the internal cavity filled with oil, a layer of 

 cell-remains, and outside all the altered cells of the mesophyl." 

 And at p. 52, he says, " the glands of the leaf occupy half or two 

 thirds of its thickness, and a layer of cells, on the external side> 

 occupies the would-be mouth of the gland." 



In '^ OiUtivated Oranges and Lemons of India," p. 206, I 

 ventured upon a suggestion in connection with the oil glands of 

 the Citrus. I said, " How could the oil cells of the Citrus first 

 have come into existence ? "Were thev oil cells from the beginning 

 of time, or were they transformations of something else ? Taking 

 into consideration that these oil cells now exist all over the bark ; 

 that the axillae or angles of the leaf-crenations contain each an 

 essential oil cell ; that the leaf -buds of Bryophyllum-calycinum are 

 produced in similar positions, and that in homologous points of 

 the pulp carpels of the Citrus seed-buds are develojied, the 

 suspicion might be raised in one's mind that, after all, these oil 

 cells — so constant in all parts of the Citrus — may not impossiblv 

 be connected with spore sacs or similar organs in some ancestral 

 cryptogamic farm ." 



At the risk of being tedious I have quoted the passage in full, 

 as I think it of some importance. I shall now proceed to show 

 that my suspicion of the true nature of oil glands is not without 

 foundation. I then thought that not improbablv they were 

 remnants of ancestral organs of reproduction, degraded or 

 atrophied, and turned to other uses in the struggle for life, when 

 more si^ecialized organs of reproduction were being evolved. 



The great struggle for existence, we should remember, is not 

 only a struggle between indi\-idual and individual, between species 

 and species, race and race, but also between parts or organs of the 

 same individual, so that some parts are degraded or atrophied, 

 Avhile others increase in size and importance of function. Such 

 phenomena in the vegetable kingdom are ver^- frequent. "We see 

 leaves degraded into tendrils, branches into spines, leaflets into 

 glands or stipels, important organs in one jDlant degraded into 

 insignificant parts in another, becoming deciduous after a brief 

 existence, or becoming wholly extinct. We even .see e.s.sential 

 organs in one plant transformed into simple hairs in another 

 and so on. 



Such is evolution — a cea.seless flow of lift', ^\\{\\ thanoe. 

 Degradation and extinction are going on in one dii-ection, while 



