495 



whilc under llic narae hc wrote: Nondum descripta. Radix parvus 



scutatus; folium infra attenuatum, sæpe spiraliter contortum, tenacius, ro- 

 J)iistius, ceterum membranaceum, tenue, palmatum vel in plures lacinias 

 irregulares divisum, margine sinuoso et crenulato«. To this description 

 he has further added the following remark: — ^1 found it in the Færoes, 

 but forpot to record it in my Tentamen«.« 



167. M. Grevillei (Thur.) Wittr. Rosenv. emend., Grønl. Havalg., 

 p. 946. Ulva plicata Lyngb., Hydrophyt., p. 30 (The specimen from 



the Færoes). 



var. typica Rosenv., 1. c. 



var. intestiniformis Rosenv., 1. c. 



var. arctica (Wittr.) Rosenv., 1. c. 



I have had a fairly considcrable quantity of this species for 

 examination and judging from it I cannot do otherwise than enlirely 

 follow Rosen vinge 's definition, an excellent one as it appears 

 to me (1. c). 



This species varies greatly in form and appearance as well as 

 in anatomicai structure: thus, not only in different transverse sec- 

 tions of the same individual, but 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 Rosen vinge. The fruiting cells often appear 

 to be drawn out Iengthwise, so that they become an elongated 

 cylinder, at right angles to the surface of the thailus. And with 

 regard to the outer form, piants 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 

 piates; and all these forms merge into one another by a series of 

 very closely connected intermediate forms. 



The specimens which I have re ferred to var. typica have fronds 

 which in a transverse section show a thickness of 15 — 27 »/. Seen 

 from the surface, the cells show slight indications of being arranged 

 in rows. The form of the thailus 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 delached 

 piants from sheltered localities. 



