8o Gibson . — Contributions towards a Knowledge of 
nur eine einfache .... Reihe von vier bis sechs Zellen Theil 
nehmen sah ’], whilst the latter believes it to arise in *S\ denti- 
culata and 5 . Galeottei from two rows of cells. It may be 
noticed at this point that Bower’s figures for .S. Martensii 
show two rows of cells in longitudinal section, not one as 
described and figured by Pfeffer. 
In the present paper I have endeavoured (a) to give a general 
and comparative account of the form and adult structure of the 
ligule, employing for that purpose alcoholic material of over 
fifty species, (b) to describe the chief stages in the development 
of the ligule in a few selected types, and (c) to hazard such 
suggestions as to the homologies and functions of the ligule in 
the genus as seem to me to be borne out by the data I have 
endeavoured to collect. 
A. Adult Structure of the Ligule. 
The ligule, in the majority of the species which I have 
examined, arises just at the junction of the stem and leaf- 
base, but distinctly from the leaf. In forms like S', oregana 
(Fig. 19), S. rnpestris 1 , &c., however, the ligule is seated in 
a deep pit in the leaf-base, and with a well-marked swollen 
region intervening between it and the stem, so as to suggest 
in some measure the foveola and ligule of Isoe/es, and the very 
deep-seated ‘ ligules ’ of allied fossil forms. 
Generally speaking, the ligule varies in outline from a short, 
somewhat rectangular plate, whose free distal margin may be 
more or less fringed with unicellular papillae, as in S.Douglasii , 
S. stenophylla , S. suberosa , S. molliceps , S. cuspidata, &c. ; or 
simply crenate, as in 5 . erythropus (Fig. 16), 5 . serpens , S. invol - 
vens, &c. ; to a distinct fan-shaped body, also with crenate, 
lobed, or papillate margin, as in S.grandis (Fig. 14), S.haema - 
lodes, S. caulescens , 5 . Karstcniana, S. viticulosa, S. plumosa , 
&c. In vS. Martensii (Fig. 13), perhaps the most perfect fan- 
shape is attained, the free distal margin being curved and 
about twice the breadth of the ligular base. Considerable 
1 In the naming of the species I have, as in previous papers, followed Baker’s 
Fern Allies. 
