477 
perhaps be found to be not quite uncommon. / 
The branching is caused by a secondary apical 
cell becoming a primary one. When the branch 
has arisen at an early moment it may give rise 
to a pseudodichotomy (fig. 440 A); if it arises 
later, it becomes feebler and the branching 
more distinctly monopodial (fig. 440 B, C). 
Opposite branches have never been observed. 
Secondary pits are produced in great 
numbers, not only in the veins but also in 
the monostromatic frond (438 C). Two pits 
may exceptionally occur in the same wall be- 
tween two cells in the latter. 
The new leaves, as is known, arise as 
adventitious shoots from the mid-rib. The first 
stages of development have not been observed, 
but the new leaves seem to arise from a super- 
ficial cell. They are at first almost filiform 
(fig. 438 D) but soon become flat. In the lower A C 
Bart of the VOTE leaves several cells early Delesseria N oe the mid-rib in 
grow downward giving rise to rhizine-like longitudinal sections. A, central cell. B, inner 
filaments that strengthen the connection with (Orlical cells showing secondary pits. C, central 
(ec) and pericentral (p) cells, the latter showing 
the mother axis and establish a union of the three secondary pits. A, € 350 :1. B 560 :1. 
conductive systems of the two axes which 
does not exist to begin with (comp. fig. 444). 
A small number of adventitious leaves may 
arise early, in spring, and grow out in the 
summer (comp. Harvey |. c.), but most of the 
leaves arise in autumn (or perhaps early in 
winter). In January they have only a small 
size, they grow out in early spring and reach 
a considerable size already in April and the 
growth ceases in the beginning of summer, 
usually in June or perhaps already in May. 
In the mid-rib the inner cortical cells 
are segregated by numerous rhizoids or con- 
ductive hyphæ (WILLE 1887 p. 59; Kyrın 1923 
! As mentioned by Kyrın (1923 p. 92), Schmitz 
/ 
and HAUPTFLEISCH's fig. 238 B, which shows a ramific- B 
ation, does not represent Delesseria sanguinea. Fig. A Fig. 440. 
according to Kyrın is a Hypoglossum, probably H. Wood- Delesseria sanguinea. From the Baltic, south of 
wardii; fig. B is probably Membranoptera alata. Als. Branched leaves. 1/4:1 
D. K. D. Vidensk. Selsk. Skr.. 7. Række, naturvidensk. og mathem. Afd. VII. 3. 61 
