78 Gibson. — Contributions towards a Knowledge of 
existence altogether. Hofmeister 1 gives by far the fullest 
account of the development of the ligule. His observations 
were made chiefly on S. denticulata , Spr., and S'. Galeottei , Spr. 
He describes it as arising from a double row of cells at the 
base of the young leaf, just in the angle between the leaf and 
the stem. These cells remain larger than the neighbouring 
cells, and have their free walls curved outwards. By alternate 
oblique segmentation of the cell lying further from the stem, 
there comes to be formed a ridge of cells with an apical meris- 
matic region lying at right angles to the long axis of the leaf 
and close to its base. Longitudinal and transverse divisions 
follow, so that the body of the ligule becomes several layers 
thick. Terminally the ligule is only one layer of cells in 
thickness, and is fringed with unicellular papillae. The cells 
by which the ligule is sunk in and attached to the leaf-base 
remain always as two parallel rows. Hofmeister describes 
the cells of the ligule as containing a granular colourless 
slime, and as being destitute of chlorophyll. He also draws 
attention to the very transitory vitality of the ligule, and to 
the fact that the development of the ligule is concluded long 
before that of the leaf to which it belongs. These two 
observations seem to be of great importance as bearing on 
the probable homologies and functions of the ligule: to this, 
however, I shall refer later on. 
Pfefifer 2 , in tracing the development of the embryo in 
S'. Martensii , makes a brief reference to the mode of origin 
of the ligule. He describes it as arising from a single row of 
four to six cells, not from a double layer, as described by 
Hofmeister ; but his account of the further development agrees 
substantially with that of Hofmeister. 
McNab 3 draws attention to the expansion of the leaf-trace 
bundle beneath the base of the ligule, and suggests that the 
ligule is an organ of absorption. 
1 Vergleichende Untersuchungen der Ent wick lung hoherer Kryptogamen. Leipzig, 
l8 5 r * 
2 Die Entwicklung des Keimes der Gattung Selaginella. Hanstein’s Bot. 
Abhandl. 1871. 
3 The Stomata and Ligules of Selaginella. Brit, Assoc. Rep. 1887. 
