24 Dansk Botanisk Arkiv, Bd. 2. Nr. 6. 



The leaves of C. antarctica are short compared with those of 

 the other Cymodoceæ etc. There seems to be a correlation be- 

 tween this fact and the elongated upright axes. The short leaves 

 stream freely in the water owing to the long stems, while in the 

 other species the axes are short and the leaves long. The leaf- 

 sheaths are compressed and conical. They fall off together with 

 the blades when the plant sheds its leaves, whereas in most sea- 

 grasses the blade alone is shed and the sheath persists on the 

 stem for a longer time. The short blade is flat and ribbon-like, 

 its margin is quite entire. At the apex two marginal teeth are 

 found and the apex itself is often emarginate (semilunate), but 

 this character is rather variable, and in the low r er leaves there is 

 little or no emargination and the teeth are absent, the apex is 

 truncate or even obtuse. This variation has misled C. A. Agardh 

 (1. c.) into making two species of his " Amphibolis" , viz.: A. bicornis, 

 i. e. the upper part of an assimilative shoot with its emarginate 

 leaf-apex, and A. zosteræfolia, a young plant with truncate leaves. 



Quite recently I. M. Black (1. c, 1915) has divided the species 

 into two, and one of the distinctive characters is the length of 

 the leaves. No doubt the length and breadth of the leaves differ 

 much in different specimens, but it seems to me to be better 

 explained by supposing that the depth at which the specimens 

 grow and the fertility of the soil have some influence in this 

 respect. In our Danish waters I have shown that such is the case 

 with regard to the variations of length and breadth of Zostera 

 leaves \ Black's new species Pectinella Griffithii is said to differ 

 from his Pectinella antarctica by its 5.5 — 9.0 cm long leaves (those 

 of P. antarctica being only 2.0 — 4.5 cm), and by certain features 

 of the female flower, but until more decisive distinctions are found 

 I think it better to regard these differences as of individual, not 

 of specific value. 



I have made measurements of the leaves of specimens from 

 different localities, also of specimens kindly sent me by Mr. Black 

 and representing both his species. In comparing these it is 

 necessary to keep the leaves of the branches of the upright 

 assimilative shoot apart from those of the main shoot itself, as 

 the latter are generally longer and sometimes narrower. 



The table given here shows a variation range from 2.0 to 

 7.0 cm. in length, and from 3.0 to 10.0 mm in breadth, but it 



1 C. H. Ostenfeld : On the ecology and distribution of the Grass-wrack 

 (Zostera marina) in Danish waters. — Report of the Danish Biological 

 Station XVI, 1908. 



