BOTAXICAI. SUBJECT?. 3^7 



reason to l>elieve tliat the oil-glands of the bark, leaves, and peel 

 of the Citrus, and similar gkuds in other plants, are mere 

 remnants of seaweed coneeptnclHs, that is persistent features 

 turned to other uses. 



Sixteenth. — It does not seem difficult, finally, to build up the 

 flower and the flower head from the simplest forms of male and 

 female orojans. I can oidy here give an outline of the process of 

 evolution (jf the liij^her forms from the lower elements. In the 

 Characea' we have the male and female elements close to each 

 other — the rudiments of stamen and ovule. In certain ferns and 

 in Lycopo<ls the sporangium is axillary. It is not difficult to 

 conceive that fusion of two or more sporangia of this kind would 

 evolve a nionu'cious head of male florets, with all the bracts 

 arranged round them, as rudiments of involucres, or se^^als and 

 l)etals. It is further not difficult to conceive that rejjrodnctive 

 male and female organs in close contiguity, such as tho.se of the 

 Characea^ calle<l ** globule and nucule," might form the founda- 

 tion of the stamen and achene in a hermaphrodite flower, sav, of a 

 Valeriana* for instance, with the hairs round the " globule and 

 nucule " developed into sepals and jjetals, and so by fusion after 

 fusion develop the cajjitulum of a composite plant. It is not 

 difficult to imagine that a one-achened and a one-stamened flower, 

 by fu.-iion with a similar one, might produce a two, three, four, 

 five-stamened and five-achened flower; and that two five-stamened 

 flowers might again create one of ten, and .so on. If, in addition, 

 in imagination, you bring into play other factors of modification — 

 atrophy, transposition, and suppression — which undoubtedlv have 

 played a great j>art in mo<lifying the external features of plants, 

 there is no vegetable form known to us, even, perhaps, the nonde- 

 script fVelwitschia, which may not be conceived to have evolved 

 out of some other j)re-existiug and allietl form. This, however, is 

 too extensive a subject to form \KiYt of a general conclusion of the 

 foregoing Xotes, and its elaboration must be left for some future 

 period. 



Summary of General Conclusion. — The reader might well 

 ask — Then is there any part of a plant which is not homologous 



* I do not mean of course the Valeriana of our days, but an ance«tral 

 Valeriana ^ 



