15 



TheZostera propagates partly by brauching as above mentioned, the branches 

 breaking loose aiid fonning independent shoots, and partly by seed. We are thus 

 led into a discussion of the flower-bearing shoots of the plant. The faet is that 

 the grasswrack is a real phanerogamous plant related to some of our laud plauts 

 and freshwater weeds, and has nothing to do with the numerous differeut kinds of 

 sea-weed (Fucus, etc), which otherwise form the vegetation of Danish \\'aters. Besides 

 the eelgrass, there is in more brackish parts of Danish waters some few other 

 marine phanerogamous piants which will be briefly mentioned later in this paper; 

 but none of them are of any importance to the biology of the sea. 



The flower-bearing shoots of the grass-wrack (I^'igs. 2 and 3) are put forth 

 in early summer; the first faint indicatious of them are seen in April — May, but 

 ouly later in the summer do the\' reach their full development. It is the tip of 

 the creeping root-stock which develops into a flower-bearing shoot: the inter-uodes 

 suddenly grow longer and grow upwards; no roots develop at the nodes; the almost 

 terete stem becomes flattened and the leaves become shorter. Theu au ample 

 ramification takes place on two sides, giving the whole flower-bearing shoot a fau- 

 like appearauce. Each branch euds iu an iuflorescence of a peculiar shape. 

 It looks as if the whole shoot ouly cousisted of leaves on whose inner 

 side the middle part is a little swolleu. Ou further investigatiou a longitudinal 

 fold is visible on this part, within which lies a flat body 4 — 6 cm. long, ou the 

 one surface of which the small flowers are placed. This body is tlie uppermost 

 part of tlie shoot and the tissured orgau by which it is enclosed is the sheath of the 

 uppermost developed leaf; its blade apparentlj' forms the tip of the shoot. The 

 structure of the flowers of which this remarkable iuflorescence is composed is 

 very simple; they consist of two rows: alteruately anthers (two oblong-pyriform 

 bodies) and pistils (a club-shaped bodj% which is fastened at the side and at the 

 pointed end split into two long, filiform appendices, the stigmas). The anthers are 

 Ihe male organs; they coutaiii an enormous (juantity of very flue threads (12 mm. 

 long by 0,008 mm. broad)') which are freed by the bursting of the anthers and float 

 about in the water. Should they meet the filiform stigmas of the pistils they 



') O. Roscnberr/ : Ueber die Pollenbildung von Zo.stera, Upsala 1901, 8. 16. 



