BOTANICAL SUBJECTS. 309 



I do not mean to say that the oil-glands of the Citrus and the 

 pores of the millipora are exactly the same thing, any more than 

 I would mean by saying that the hand of a man is the same thing 

 as the forefoot of a lizard. What I do mean is that, taking into 

 consideration the evolution of the higher animals and plants from 

 the lower, and the branching off of both from the jDrimitive unicel- 

 lular bodies, together with the force of heredity, there would be 

 sufficient ground for looking upon the surface of the Citrus leaf, 

 with its large and small dots, as having some distant relationship 

 with the surface of the millipora, with its similarly disposed and 

 similarly sized dots. The one suited to a life in the bottom of the 

 sea, the other suited to an air life, with totally different 

 surroundings and functions. 



I have pointed to the millipora in order to explain in some 

 way the different sizes, and the disposition of the oil-glands in the 

 Citrus leaf, but it is with the conceptacles of the Fucus, Sargassum, 

 and other seaweed fronds that I would claim for them a homology. 



The minute anatomy of the Fucus conceptacles of course 

 differs from that of the oil-glands, but as I consider the latter as 

 " persistent structures with altered function," this need not 

 surprise us. It only requires a thorough belief in evolution, with 

 inheritance of certain parts, together with a certain power of 

 imagination and freedom from dogma, to bring the two on the 

 same level of a common origin. The conceptacle no longer being 

 needed as a reproductive organ is modified into an essential oil- 

 gland to serve another purpose in a surrounding of insects. 



This same hypothesis, viz., of descent from a jPwcM5-like plant, 

 may account for the oil-glands on the Citrus 6ar^, For originally 

 the stem was a cladophyl, like that of Delesseria (Fig. 12). The 

 blades of the petiole and leaflet are the survivals of a winged stem, 

 and the midrib is a dwarfed representative of a branch of that 

 ancient Fucus-like ancestor, the oil-glands on both sides of the 

 Citrus leaf being the modified descendants of the barren con- 

 ceptacles of the Fucus frond. 



All this may, however, seem to the reader a pack of absurdities. 

 If so, all I can say is — I cannot help that. I do not lay any claim 

 to being the inventor of the theory of Evolution. I am only 

 humbly trying to apply its principles in explaining the presence 

 and disposition of the Citrus oil-cells, placed all over its surface 

 with the same regularity of the pores in the millipora. 



