495 
while under the name he wrote: — »Nondum descripta. Radix parvus 
6cutatus; folium infra attenuatum, saepe spiraliter contortum, tenacius, ro- 
bustius, ceterum membranaceum, tenue, palmatum vel in plures lacinias 
irregulares divisum, margine sinuoso et crenulato«. To this description 
he has further added the following remark: — »I found it in the Faeroes, 
but forgot to record it in my »Tentamen«.« 
167. M. Grevillei (Thur.) Wittr. Rosenv. emend., Gronl. Havalg., 
p. 946. Ulva plicata Lyngb., Hydrophyt., p. 30 (The specimen from 
the Faeroes). 
var. typica Rosenv., 1. c. 
var. intestiniformis Rosenv., 1. c. 
var. arctica (Wittr.) Rosenv., 1. c. 
I have had a fairly considerable quantity of this species for 
examination and judging from it I cannot do otherwise than entirely 
follow Rosenvinge’s definition, an excellent one as it appears 
to me (1. c.). 
This species varies greatly in form and appearance as well as 
in anatomical structure: thus, not only in different transverse sec¬ 
tions of the same individual, hut in one and the same transverse 
section, cells may occasionally be met with which are sometimes 
longer, and sometimes shorter than they are broad, as has also 
been pointed out by Rosenvinge. The fruiting cells often appear 
to be drawn out lengthwise, so that they become an elongated 
cylinder, at right angles to the surface of the thallus. And with 
regard to the outer form, plants are met with which are sometimes 
only a few cm. in height and more or less folded, sometimes funnel- 
shaped or tubular, or they may occur in the form of very large 
plates; and all these forms merge into one another by a series of 
very closely connected intermediate forms. 
The specimens which I have referred to var. typica have fronds 
which in a transverse section show a thickness of 15—27 y. Seen 
from the surface, the cells show slight indications of being arranged 
in rows. The form of the thallus is rather variable, being some¬ 
times divided into few or more segments with the saccate basal 
part hardly discernible; and sometimes only slightly divided so 
that they are almost funnel-shaped, the latter specimens approaching 
var. Vahlii (J. Ag.) Rosenv. But I have not met with quite typical 
specimens corresponding with the Greenland specimens of this variety. 
Lastly, large plate-formed specimens occurred, generally in detached 
plants from sheltered localities. 
