the Anatomy of the Genus Selaginella , Spr. T25 
than those of the aligular face, as in S. Lyallii , .S. cnspidata , and 
pilifera. In the majority of the species the epidermis of the 
ligular face consists of polygonal cells almost or quite isodia- 
metric, and appearing conical in transverse sections of the leaf, 
whilst the epidermis of the aligular face consists of elongated 
cells rounded or quadrate in section. Russow further points 
out that with regard to the smaller (dorsal) leaves, the cells of 
the ligular face correspond to those of the aligular face of the 
larger (ventral) leaves, and those of the aligular face of the 
smaller leaves to the cells of the ligular face of the larger 
leaves. The elongated epidermal cells contain several small 
chloroplastids, the conical cells generally two, or occasionally 
three, chromatophores only. In some species (e. g. 5. Kraus - 
siana) a layer of conical cells occurs beneath the epidermis 
of the ligular surface of the larger leaves and of the aligular 
surface of the smaller leaves, whilst in S. Lyallii this rudi- 
mentary palisade-layer becomes well marked. Stomata are 
described as occurring only on the aligular face, but ex- 
ceptionally in S. pubescens (= S. Braunii , Bak.) stomata 
occur on both surfaces of the smaller leaves 1 . Of the species 
mentioned by Russow as having stomata on the aligular 
surface only, I have examined all, and have been somewhat 
surprised to find that no less than three of them, viz. 5. 
Kraussiana , S. cuspidata , and S . pilifera, had stomata on both 
sides of both dorsal and ventral leaves. Lastly, Russow calls 
attention to the peculiar cells of the epidermis of the ligular 
face of the larger and the aligular face of the smaller leaves 
(Doppelkegeln) in 5. uncinata , and to the development of 
sclerotic fibres at the margins and on the surface of certain 
species, e. g. S. Martensii and 5. stenophylla . 
Treub 2 has studied the mode of development of the leaf in 
S. Martensii . His results agree in the main with those of 
1 1 Bei S. pubescens finden sich. auf beiden Flachen der kleinen Blatter Stomata ; 
bei alien iibrigen untersuchten Arten war nur die Epidermis der Aligularflache, 
sowohl bei grossen als kleinen Blattern, mit Spaltoffnungen versehen.’ Russow, 
1. c., p. 138. 
2 Les Organes de la Vegetation du Selaginella Martensii, Spr. Leide, 1877. 
