ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 485 



Genus Platycerium.* — H. v. Straszewski writes on the morphology, 

 anatomy and physiology of the genus Platycerium. The gametophyte 

 shows great similarity with that of Cyatheaceaj ; forked prothallia, 

 many -celled glandular hairs, and divided cap-cells in the antheridium 

 all point to Cyatheacese. The cells of the root-cortex show a similar 

 thickening to the cells of the roots of Orchidaceas ; they are capable of 

 absorbing water tlirough the cortex. Also the intercellular spaces of 

 the basal fronds (" Mantelblatter" and "Mantelnischenblatter") contain 

 water. The " Mantelblatter " when young show a negative geotropic 

 curvature, which is corrected later by epinasty. This epinasty obliges 

 the leaves to lie flat on the substratum. The ground tissue of the 

 " Mantelblatter " consists only of spongy parenchyma. The hypoderm 

 is a non-mucilaginous water-tissue. The " Mantelnischenblatter " and 

 " Mantelblatter " are phylogenetically older than the " Laubblatter," 

 The " Mantelblatter " have developed from the " Mantelnischenblatter." 

 Platycerium does not belong to the Acrostichese, and has nothing to do 

 with Gheiropleura. Its best position is among Polypodiacese. The 

 author divides Platycerieae into three geographical groups, and considers 

 the grouping of Fee and Diels to be wrong. The three groups are : 

 (1) South American region with one species {P. andinum) ; (2) the 

 African region with five species ; and (3) the Asiatic and Australian 

 region with eleven species. The author goes into the question of leaf- 

 dimoi-phism with much detail. 



_ New Varieties of Nephrolepis-f — R. C. Benedict discusses the 

 origin of new varieties of Nephrolepis by orthogenetic saltation. The 

 variations are discontinuous and large, and they also occur along a few 

 limited lines. 1. The genus is tropical ; and nearly all its species tend 

 to vary under cultivation, but N. exaltata in particular has through its 

 variety hostoniensis been especially prolific of new forms ; at least some 

 sixty named horticultural forms have been recorded, and probably as 

 many more remain unnamed. The great majority of these have arisen 

 from bud-sports ; for the reproduction is almost exclusively vegetative. 

 The present paper is limited to the more pronounced lines of progressive 

 variation. 2. Cultural conditions favour the appearance and preserva- 

 tion of variations. 3. The variations are of two sorts — progressive and 

 regressive. 4. Progressive variations have followed three main lines, 

 viz. increased division of leaf, or ruffling of pinnae, or dwarfing. Also 

 dichotomy may occur. 5. Progressive increase in division has gone on 

 for five vegetative generations ; ruffling for three ; dwarfing for three. 

 6. Dwarfing is of two sorts : first, brachyotic or unilinear ; and second, 

 normal in all directions. Also more than one type of division-sport 

 is found. 7. Progressive increase in leaf division and progressive 

 dwarfing may always be expected until the possible limit has been 

 reached. 8. Regressive variations rarely if ever show complete return to 

 their parent forms or to var. hostoniensis. 9. The indicated coefficient 



* Flora, cviii. (1915) pp. 271-310 (42 figs.). See also Bot. Centralbl., cxxxii. 

 (1916) p. 39. 



t Bull. Torrey Bot. Club, xliii. (1916) pp. 207-34 (6 pis.). 



Oct. 18th, 1916 2 L 



