Page. 

 XIV.— Trichomes, PpvICKltes, Glandular Hairs, Sporangia, 

 &c. 277 



Spathels of Jonquil are tricliomes— Trichomes aud tentacles of 

 Drosera are one thing — The epidermis not essentially distinct 

 from the structures below it — Antheridia aud spores of sea- 

 weeds are trichomes — Oogonium corresponds to a metamor- 

 phosed hair — Vascular bundles not necessary to reproductive 

 organs — Glandular hairs comparable to reproductive hairs, 

 and also to pollen and ovules — ]S^o distinction between 

 prickles, glandular hairs, and eveu spines — Lenticels possibly 

 atrophied prickles — Teeth of leaves only glandular hairs with 

 a foliaceous stem, like those of the moss-rose — Globular 

 hairs of leaves homologous with pollen and ovules — The 

 ramelli of Dasga sarcocaidon and others are only branched 

 hairs — Glandular hairs found also in intercellular spaces — 

 Glandular hairs of Drosera convertible into ovules, leaves, 

 and branches — Hairs of Begonia Phi/llomaniaca convertible 

 into branches — Reproductive organs of Cymopolia barbata 

 and Fuais are only hairs — Teeth of Agave and similar 

 plants are only modified branches — Teeth of Desmaretia 

 convertible into branches. 



XV.— Oil Glands and Figs - - - - - 299 



Description and histology of an oil gland— Oil gland probably 

 a degenerated conceptacle of the seaweed — Analogous 

 degradations found in many plants — Conceptacles of 

 Myviodesma, Fuciis, &c. probably the grand-ancestors of 

 oil glands — Conceptacles of different species of Fiicns — Oil 

 glands considered as remnants of conceptacles turned to 

 another purpose — The orange tree related to a Fncus — Like 

 the splint-bones of the horse, the oil glands are remnants of 

 former important organs — Oil glands of Citrus peel analo- 

 gous to pores of MilUpora. The fig (receptacle of Ficus) is 

 only a further development of the conceptacle of Fucus — 

 Both are moncecious and dioecious. 



XVI.— Spurs - - - - - - - 317 



Are spurs the result of insect agency or of natural selection ? — 

 Spurs on petals and leaves can be spontaneously produced, 

 without either of the foregoing agencies — Do spurs always 

 contain nectar, or do they sometimes contain only water? 

 — Teratological variations in Aquileyia aud Aconitnm. 



XVII. — Genesis of Firro-vascular System - - - 325 



Rudimentary spiral threads in Alga? — Spiral microbes of 

 bacteriologists — Possibility of these gaining access to 

 cellular plants, and laying the foundation of the vascular 

 tissue — Two ways of viewing the origin of the vascular 

 tissue — Few operations connected with life appear to be free 

 from the influence of microbes. 



