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



one leaf and one root appear. The rhizome branches freely, 

 especially where flowers are found, and here, sometimes elsewhere, 

 parts of the rhizomes have short internodes (in C. nodosa, which 

 is best known, each zone of short internodes is said to correspond 

 to the wintertime). The flower is solitary and terminal; it is in- 

 closed in a leaf similar to the others, while a bud in the axil of 

 the uppermost leaf but one develops into the prolongation of the 

 main axis; thus the growth of the flowering rhizome becomes 

 sympodial, whereas the infertile rhizome is a monopodium. Each 

 lateral shoot begins with a blade-less sheathing leaf, placed with 

 its dorsal side against the main axis. The ordinary leaves have 

 an open (split) compressed sheath which incloses the basal parts 

 of the younger leaves, or the flower. At the apex the sheath is 

 somewhat biauriculate ; it varies in width from 3 to 7 mm and 

 is wider in the upper part, narrower towards the base. The 



Fig. 2. Cymodocea angustata. 

 Transverse section of a leaf-blade. To the left the marginal part with a 

 marginal sclerenchyma-strand and two side- veins; to the right the central 

 part with the mid-vein. Tannin idioblasts dotted; x lacunæ. (About 125 li 



nat. size.) 



leaf blade is shorter and broader than in C. rotundata and C. nodosa, 

 longer and narrower than in C. serrulata, the proportions being 

 15 — 20 cm (in a single shoot 60 cm) long and 3 — 6 (mostly 4 — 5) 

 mm broad. In its upper part the width of the blade decreases 

 regularly towards the obtuse tip, the margins being distinctly 

 serrulate, especially at the apex. 9 — 13 parallel nerves run through 

 the blade, besides two marginal sclerenchyma-strands (Fig. 3 a). 

 The surface of the whole leaf is very finely spotted by cells of a 

 red-brown colour containing some tannic compound ("cellules 

 sécrétrices", Sauvageau). 



The place where the blade and sheath meet is distinctly 

 marked and the blade breaks off easily, leaving the sheath per- 

 sistent for some time. 



As to the anatomy of the leaves, there is great resemblance be- 

 tween C. nodosa, C. rotundata and C. serrulata as shown by P. Magnus x 

 and C. Sauvageau x ; C. angustata does not differ in any essential 



1 P. Magnus, in Sitz. ber. d. Ges. naturf. Freunde, Berlin f. 1870, p. 85. 



