485 
into an ordinary branched frond. The stipe is fixed to the substratum by a conical dise 
united rhizines. Adventitious shoots early appear in the stipe. 
formed by densely 
The antheri- 
dia occur, as shown 
by BurrHam (1893 
p. 296 figs. 22—24) 
in minute leaflets 
arising from the 
apices of the plant 
and, especially, in 
groups from the 
axils (comp. KYLIN 
1923 fig. 69a); they 
cover the whole sur- 
face except a mar- 
ginal zone which is 
sometimes very nar- 
row, and the lower 
portion of the leaflet 
may also be sterile 
) COX S MI STE a SS C RS Oo Z 
TIS TERING to 
ÉTANG 
ee 
Ÿ O DO 
Pe ee Oa EEE 
Weta tele Te 
DS SOEEEN 
Fig. 452. 
Membranoptera alata. Tip of the plantlet represented in fig. 451 A. The figures indicate 
the number of segments from the top. 350: 1. 
(fig. 453). According to Kyrın, the development and structure of 
the spermatangia and the spermatia is similar to that in Apoglossum ruscifolium. 
The procarps arise in the mid-rib in adventitious shoots or in the upper part 
of the frond; their development has been described by PrırLırs (1898) and Ky in 
Fig. 453. 
Membranoptera alata. Male leaflets. 
(1923). The cystocarps occur singly on the mid- 
rib in the said parts of the frond. 
The tetrasporangia occur in sori in adventitious 
branchlets or in the ultimate branches of the frond. 
According to Kyrın (1923 p. 113), they develop 
from superficial cortical cells in the same way as 
in Delesseria. 
Membranoptera alata occurs in all the Danish 
waters except the fjords and perhaps the waters 
around Bornholm where it has only been met 
with as washed ashore. It reaches a length of 
14 cm in the Northern Danish waters, 12 cm in 
the Sound and the Belts, 8 em in Bw, 7 em in Bm 
and 5 cm in Bb. The breadth is rather variable. 
In the northern waters it usually varies about 2 mm, it frequently amounts to 3 mm 
more rarely to 4,5 mm. In the Great Belt and the Sound a breadth of 3,5—4 mm 
may still be reached in deep salt water. In Bw it is rarely more than 2 mm broad, 
in Bm !/,—1 mm (in one specimen 1,5 mm). A specimen from Bornholm was only 
0,3 mm broad (comp. Plate VII figs. 5—7). 
D. K. D. Vidensk, Selsk. Skr., 7. Række, naturvidensk. og mathem. Afd, VII, 3. 62 
