20 Mitchell ’ — Contributions towards a Knowledge of the 
The material examined comprised thirty-eight species, for which I am 
indebted to Professor Harvey-Gibson, who placed his collection at my dis¬ 
posal ; I am also indebted to the Director of the Royal Gardens, Kew, 
who kindly forwarded me fresh material of vS. Lyallii and S. Wildenowii. 
The literature referring to the cone of Selaginella , apart from the 
development of the gametophyte. is very scanty. Goebel, Schwendener, 
Steinbrinck, and others have investigated the structure of the sporangium 
wall, with the view of ascertaining the mechanism of spore discharge. The 
recent researches of Miss Lyon on S. apus and S', rupestris have demon¬ 
strated very clearly the progress Selaginella has made in the direction 
of the seed habit. The study of the cone is, however, specially interesting 
as supporting in some measure the theory advanced by Professor Bower as 
to the origin of the strobilus in Archegoniate plants. It is, of course, not to 
be expected that an investigation of Selaginella , a type essentially spe¬ 
cialized in having acquired a definite strobilus and heterosporous habit, can 
be as enlightening as a study of the simpler Lycopodinae, but detailed exami¬ 
nation has revealed numerous examples of reversions to more primitive 
conditions, such as branching of the fertile region, alternation of sterile and 
fertile portions in the strobilus, continued apical growth beyond its apex, 
re-establishment of dorsiventrality, &c., and the occasional occurrence of 
sporangia in the axils of purely vegetative leaves, all of which anomalies are 
not only easily explained on Bower’s hypothesis of the evolution of the 
sporophyte, but would naturally be expected to occur, and are to be 
read as emphasizing the phylogenetic affinity between the Selaginellaceae 
and the Lycopodiaceae, and confirming the assumption that the former are 
but specialized derivatives of the latter. 
The following is a list of all the papers I have had occasion to consult, 
and these will be referred to in the text by the prefixed numeral:— 
1. Bower: Origin of a Land Flora, 1908. 
2 . -: Abnormal plurality of sporangia in Lycopodium rigidum. Annals of Botany, xvii, 
I 9°3- 
3 . -: Imperfect sporangia in certain Pteridophyta—are they vestigial ? Annals of Botany, 
xv, 1901. 
4 . -: Theory of the Strobilus in Archegoniate plants. Annals of Botany, viii, 1894. 
5 . -: The Morphology of spore-producing members. (Equisetales and Lycopodiales.) 
Trans, of Royal Society, Ser. B. clxxxix, 1897. 
6. Lyon, F. H. : Sporangia and gametophytes of S. apus and S. rupestris. Botanical Gazette, 
xxxvi, No. 4, 1903. 
7 . -: Another seed-like characteristic of Selaginella. Botanical Gazette, xl, No. r, 1905. 
8. -: Two megasporangia in Selaginella. Botanical Gazette, xxxvi, No. 4, 1903. 
9. Goebel : Sporangien, Sporenverbreitung und Bliithenbildung bei Selaginella. Flora, lxxxviii, 
1901. 
10. Steinbrinck : Ueber den Schleudermechanismus der Selaginella- Sporangien. Berichte der 
deutsch. bot. Ges., xx, 1902. 
11 . Schwendener : Ueber den Offnungsmechanismus der Selaginella- Sporangien. Berichte der 
deutsch. bot. Ges., xxi, 1903. 
