Conducting Tissue- System in Bryophyta. 5 
The occurrence of a strand of elongated lignified thick- 
walled cells in the midst of a Liverwort-thallus was first 
discovered by Sir William Hooker (British Jungermanniae 
1816) in Jungermannia (now P allavicinid) Lyellii . Gottsche 1 , 
in 1864, describes a similar strand in Symphyogyna sinuata , 
N. et M., and states that there are often two such nerves at 
the base of the frond, which run parallel for some distance 
and often diverge at the first bifurcation of the thallus. 
He found that the strands had no connexion with the 
‘ receptacles ’ on which the sexual organs were seated. Leitgeb 
in Heft 3 of his classical f Untersuchungen fiber die 
Lebermoose ’ describes the cells of this strand in Sym- 
phyogyna , and states that Blyttia (P allavicinid) and Umbra- 
culum ( Hymenophyton ) have similar strands. He mentions the 
interesting fact that in the common formation of adventitious 
branches from the ventral side of the frond in these genera, 
the strand of the branch is discontinuous with the strand of 
the parent frond. He describes the cells of the strand as 
being elongated with pointed ends and fairly thick walls, 
provided with close-set ‘ pores/ which are arranged in spiral 
lines round the walls, so as to give the impression of spiral 
thickening on casual examination of a longitudinal section. 
Haberlandt 2 refers to Leitgeb’s ^descriptions, and expresses 
the opinion that the strand in question may very probably 
possess both a mechanical and a water-conducting function. 
Spruce 3 describes and figures a new species of Symphyogyna 
from Dominica, which he names S', trivittata on account 
of the three strands running parallel in the midrib of the 
thallus. Sometimes there are only two in the upper parts, 
owing to the running off without branching of one of the three 
at a bifurcation, in the same way as in S. sinuata . 
Farmer 4 , in a study of Pallavicinia decipiens , Mitten, de- 
scribes the strand of the rhizome of this plant as consisting of 
1 Triana and Planchon’s Prodromus Florae Novo-Granatensis. Ann. Sci. Nat., 
5 e ser., tome i, p. 182. 
2 Beitrage zur Anatomie und Physiologie der Laubmoose, 1886, p. 378, note. 
3 Hepaticae Fdliotianse, Journ. Linn. Soc., vol. xxx, 1893-5. 
4 Studies in Hepaticae. Annals of Botany, viii, 1894. 
