The Botany of Iceland - 01.12.1928, Blaðsíða 65

THE AERIAL ALGÆ OF ICELAND
389
Navicula Brekkaensis Boye P. n. sp.
Valva lineari, in medio inflata, apicibus rotundatis. Area
centrali quadrata, area apicali angusta, long. 10—18/i, lat. 3,4—
3,9 /t, striis delicatissimis, mediis radiantibus, circ. 36 in 10 /t,
ceteris parallelis, densioribus. Fig. 16.
N. Icel. 92, 169, 218, 254 - W. Icel. 336.
Fig. 16.
It bears a close resemblance to N. contenta, from which, B^^cula.
however, it deviates in several respects. The apices are al~ Boyep'iTsp
ways simply rounded, not capitate, the striæ, which, by the (x 1200).
way, are very difficult to detect, are coarser in the inflated
central part than in the remainder of the valve, and radiate in this part,
while they are parallel in the other parts. Furthermore, N. Brekkaensis
has a distinct square central area.
I have found it in very diverse localities and never in any great
number of individuals, so it is difíicult to form an idea as to what life
conditions are most favourable to it.
Navicula Kotschyi Grun. Cl. Syn. I, p. 130. N. Ivotschyana
V. Heurck Syn. Pl. 10, fig. 22. Fig. nostr. 17.
E. Icel. L. 129.
On a rocky wall in Vestdalur near Seyðisfjörður I found
this species in great number. Originally it was found in hot
springs near Buda-Pest. Later on it is recorded from the
Bodensee and other lakes in Central Europe and from a damp
rocky wall (v. Schönfeldt, 1913, p. 80), and flnally Hustedt
found it in a rock cave in Silesia in company with Pinnnlaria
borealis and Navicula contenla (1922, p. 98). Hence there can
hardly be any doubt that it thrives well as an aérial alga,
especially on damp rock.
Hustedt points out (1. c.) that in reality it has an iso-
lated point in the central area, like Navicula mutica. I can
confirm this, baving found a well-marked dot in the central
area which formed the termination of a faint line of small puncta. The
same is seen in V. Heurck’s figure above referred to. The specimens
found by me were somewhat larger than those mentioned in Cleve’s
diagnosis viz. up to 33 fi in length, 9,0 in br., whereas the number of
the striæ agreed with Cleve’s statements, being 18 in 10/i in the
middle an 23 near the apices.
Fig. 17.
Nauicula
Kotschyi
Grun.
(X 1200).
Navicula mutica Kútz. sp. collectiva.
This species was originally established by Kutzing, and the type is
regarded by V. Heurck (Syn. Pl. 10, flg. 19) as being most probably
what we now call f. Göppertiana.
The species comprises a great number of different forms all known
by their distinctly punctate striæ (commonly 18—20 in 10 p), and a
distinct transapical area with an isolated point on one side of the cen-
tral nodus.
The Botany of Iceland. Vol. II.
26