ZOOLOGY AND BOTANY, MICROSCOPY, ETC Gl 



mode of formation. The author still maintains his opinion that the 

 ■secretory cells of Ginkgo are mainly, if not entirely, lysigenous in origin. 



Anatomy of Embryo of Cannaceae and Musaceae.* — C. L. Gatin 

 lias studied the embryology and germination of the Cannaceae and 

 Musacese, and finds that in both cases the embryos are remarkable for 

 their advanced state of differentiation. Their radicle is less endogenous 

 than that of the palms, being least so in Strelitzia, where the piliferous 

 layer is continuous with the subepidermal layer of the embryo. Heli- 

 conia, however, has a very poorly differentiated embryo, and the central 

 cylinder is differentiated before other parts of the radicle, thus approach- 

 ing the palms more nearly than the other Musaceos. The cotyledon is 

 much larger than in the palms owing to the greater size of the individual 

 cells. There are two phases in germination : (1) the elongation of the 

 cotyledon ; (2) germination proper. The arrangement of the cotyle- 

 donary bundles does not favour the views of those writers who regard 

 the single cotyledon as derived from the fusion of two ancestral 

 cotyledons. 



Adventitious Roots of Dicotyledons. f — Dr. Noll contributes a 

 short note upon the adventitious root-system of Dicotyledons. Tin: 

 theory which regards the acropetal succession of rootlets as the rule 

 among Dicotyledons, appears to be untenable in the light of the present 

 work. The presence of an adventitious root-system has been proved 

 to exist in Helianthus, Ricinus, Cucurbita, and the female plant of 

 Cannabis, and the author is of the opinion that an adventitious root- 

 system may be as readily developed among Dicotyledons as among 

 Monocotyledons when the disproportion between the aerial portions of 

 the plant and its root-system renders such development necessary, but 

 that while in Monocotyledons the adventitious root-system will be in 

 connection with the growing stem, in Dicotyledons it will be connected 

 •with the root. 



Leaf-structure of Sand-dune Plants of Bermuda.^— J. W. Harsh- 

 berger describes the sand-dune plants of Bermuda, with special reference 

 to the modification of leaf -structure. The most important ecological 

 factor appears to be the bright illumination from above, and the reflec- 

 tion of light from the white sand below, and the light stimuli have 

 produced changes in both the form and the structure of the leaves. The 

 most important modifications include thick cuticle in Nerium Oleander, 

 Conocarpus, etc.; thick epidermis in Ganavalia, Dodoncea, Ipomoca pes- 

 caprce, etc. ; two or three epidermal layers in Conocarpus, ' 'roton, etc ; 

 several rows of palisade-cells in Passijtora, Conocarpus, etc.; depressed 

 stomata in Sisyrinchium, Sesuvium, etc. ; stomata in pits in Lantana 

 and Nerium ; succulent leaf in Sesuvium i Conocarpus, etc ; hairy leal 

 in Borrichia, Toumefortia, etc.; varnished leaf in Dodoncea-, erect 

 position of leaf in Stenotaphrum, etc. ; overlapping leaves in Euphorbia, 

 •etc.; latex-tissue in Euphorbia >,; gum-resin in Conocarpus; crystals in 

 Croton, etc. ; modification of mesophyll in many genera, including 

 Ipomoca, Passiflora, Conocarpus, etc. 



* Ann. Sci. Nat., ser. 9, viii. (1908) pp. 113-46 (2 pis. and 34 figs.). 



t S.B. Natur. Ver. Rheinl.. ii. (1907) pp. 54-7. 



t Proc. Amer. Phil. Soc. xlvii. (1908) pp. 97-110 (3 pis.). 



