86 Recent Discoveries of Pteridophyte Prothalli. 
advance in this subject. He described 1 the prothalli of Lycopodium 
ceniuum, L. salakeuse , L. Phlegmaria, L. carinatum , Z. nummulari- 
folium and L. Hippuris, and shewed that these tropical species could 
be assigned to two very distinct types of gametophyte within the 
genus, (i.) the type of L. ceniuum , in which the prothallus is an 
upright green cylindrical structure with marginal lobes on the edge 
of its expanded summit, and autophytic, ( i.c . doing its own assimi¬ 
lation by means of its chlorophyll), and (ii.) the type of L. Phleg- 
mavia , which has a colourless branched cylindrical structure and is 
saprophytic in humus on tree trunks. Besides these there was the 
already partially known type of the European L. inundatum. In 
1898 Prof. Bruchmann of Gotha published a full account 2 of the 
prothalli of several European species of Lycopodium , including 
L. clavatum, L. annotmum, L. complanatum and Z. Sclago, all of which 
are subterranean and saprophytic, though they turn green if culti¬ 
vated on the surface of the soil, and showed that five types can be 
distinguished within the genus. This variety in the form and habit of 
the gametophyte in a single genus is a remarkable fact, in striking con¬ 
trast with the great uniformity of the sporophyte, which in all known 
species of the Club-mosses is extremely similar in appearance and 
anatomy. So impressed, indeed, was Bruchmann with this diversity in 
the gametophytes of the different species that he proposed to separate 
the genus Lycopodium into several distinct genera according to the 
structure of the gametophyte, and suggested that the similarity of 
the sporophytes should be explained as the result of convergent 
adaptation. This conclusion has not, however, been generally 
accepted. In the same year, Dr. W. H. Lang, of Glasgow, indepen¬ 
dently discovered the prothallus of Lycopodium clavatum as a result 
of careful search in the mountains near Clova, in Forfarshire. In 
his account of his observations 3 he criticises Bruchmann’s views 
and points out that in a very old and cosmopolitan genus like 
Lycopodium , the adaptation of the prothallus to various conditions of 
environment has very likely been an important factor in enabling 
the plants to maintain themselves in the struggle for existence, and 
that consequently the great diversity of the prothallus in different 
species, exceptional though it appears to be, is not surprising. 
In pursuit of his researches on the gametophytes of the Vas¬ 
cular Cryptogams, Dr. Lang undertook, in 1900, an expedition to 
1 Aim. du. jard. hot. de Buiteiizorg, vols. iv., w, vii., 1894,-6,-8. 
2 Ueber die Protliallien und die Keimptlanzen melirerer 
europaisclier Lycopodien Gotha, 1898. 
3 O11 the Prothallus of Lycopodium clavatum.—Ami. of hot., 1899. 
