49 2 Boodle.-—Anatomy of the Hymenophyllaceae. 
Russow 1 gives a rather general description of the anatomy 
of stem and petiole in the Hymenophyllaceae. In the stem 
he mentions that the tracheides form a compact mass in some 
species, but are separated from one another by conjunctive 
parenchyma ( Geleitzellen ) in others. The protoxylem-elements 
are given as being scattered in numerous groups over the 
whole transverse section of the xylem, and it is represented 
so in a diagram of Trichomanes radicans (Taf. X, Fig. 6). 
The outer phloem-elements are regarded as being probably 
protophloem, and the roots are described as varying from 
monarch up to octarch. The elements like bast-fibres, which 
occur in petiolar bundles of T. Prieurii , &c., are regarded as 
morphologically similar to those in some Gleicheniaceae and 
Schizaeaceae. Prantl 2 devotes much attention to the venation 
of the leaves in the Hymenophyllaceae, and comes to the 
conclusion that a study of their habit points to the develop¬ 
ment having proceeded from simple plants with small undivided 
leaves to the more complex types. Several of Prantl’s 
anatomical results have been referred to above. Potonie 3 
states that in Hymenophyllum nitens the common origin of 
endodermis and pericycle (several cells thick) is placed beyond 
doubt by the arrangement of the cell-walls in the mature 
rhizome. He regards the protophloem of Hymenophyllaceae 
as being very probably sieve-tubes. In H. nitens he finds 
f Liickenparenchym ’ present. The structure of the petiole 
is described in a large number of Ferns by Thomae 4 . In 
describing T. radicans , he mentions that in the lower part 
of the petiole there is a round vascular bundle, with annular 
xylem, but that, further up, the ring opens on the upper 
side, and the bundle becomes heart-shaped. He states that 
the part shut in by the ring consists only of parenchymatous 
cells, so like Prantl he overlooked the internal tracheides. 
1 Russow, Vergleich. Untersuch. d. Leitbiindel-Kryptogamen, Mem. de l’Acad. 
Imp. de St. Petersbourg, vii, 19, 1872, p. 94. 
2 Prantl, Unters. z. Morph, d. Gefasskryp., I. Hymenophyllaceen, 1875. 
3 Potonie, Zusammensetzung der Leitbiindel, Jahrb. d. k. bot. Gart. Berlin, II, 
1883. 
4 Die Blattstiele der Fame, Pringsheim’s Jahrb., xvii, 1886. 
