26c 



latter having fewer stomata upon the upper surface and none 

 at all upon the lower surface.^ 



4. TrachijphfjUnm. 



The three species which have been examined, agree in 

 (1) the structure of the hydathode (it opens upon the upper 

 surface of the leaf, with flattened or highly convex epithema; 

 hydathode-cavity absent), (2) the structure of the hairs (they are 

 everywhere irregularly-multicellular and retain this feature, either 

 they have, or are without, an apical gland, — in contradistinc- 

 tion to the sections Boraphila, Nephrophijllum, Dactyloides), 

 and (3) the cells of the spongy parenchyma are very little or 

 not at all branched. — The three species differ most in the 

 form of their leaves, but are separated also by other, smaller 

 differences. 



The chief structural features useful in diagnosis are the 

 following: — 

 Leaves: — 



toothed at the apex, with three acute teeth: S. tricuspidata. 

 entire: — 



margin hairy along the lower half of the leaf: S. 



aizoides, 

 margin hairy along its whole extent: S. flagellaris. 

 Hairs: — 



irregularly-multicellular marginal hairs: 6\ aizoides, 

 glandular hairs with irregularly-multicellular stalks: 6\ 

 flagella7'is, 



(1) with globular head: S, flagellaris, 



(2) with club-shaped head: <S. tricuspidata. 



^ Besides the principal form I also examined specimens of tlie variety 

 palmaia from Tliingvellir in Iceland (June 13, 1895). The latter is very 

 remarkable by reason of its agreeing in almost all points with S. hypnoides 

 in regard to leaf-anatomy; the only dilference being that a few of the 

 marginal hairs of the leaf are glandular. 



