16 



fasten on them, and a fertilisation of the female organ, the ovule which is enclosed 

 in the pistil, is effected. The fertilisation is thus brought about by means ot the 

 water, a peculiarity only very seldom seen in the phanerogamous plauts. In eon- 

 formity with this the pollen of the anthers is shaped like fine threads, whereas 

 in the planerogamous piants it generally consists of small round grains. The 

 anthers of one inflorescence of the Zostera cannot fertilize the pistils of the same 

 inflorescenee, as the latter develop first and the time within which they are receptive 

 of fertilisation is over when the anthers open; it is thus evident that fertilisation must 

 be effeeted by pollen from other infiorescences, one stage ahead in development. 

 Fertilisation having been effeeted, the pistil gradually swells and inside it one single 

 seed develops, which when ripe is ca. 3 mm. by 1,5 mm., cylindrical in shape with 

 rounded ends and of a gray-brown or yellow-brown tinge; the sliell of the seed has 

 faint longitudinal stripes. When the seed is ripe the pericarp opens by a longitudinal 

 fissure, so that the seed mav slip out; the pericarp itself is rather thin, juicy 

 and soft. 



The freed seeds sink to the bottom of the water (or they are perhaps 

 sometimes swallowed by fishes, through the alimentary tract of which they pass 

 uudigested). The current carries them away to other piaces wliere they form new 

 growths of eel grass. The germinatioa probably takes place in the following spring; 

 I have at any rate found seedlings in July — August which were probably not a 

 year old, as they had not yet put forth any visible creeping shoot. These young 

 seedlings are however only very seldom to be seen, mostly due to the faet that 

 they do not generally come loose together with the larger shoots of the eel-grass 

 when these are torn from the bottom, and a direct investigation of the place 

 where the Zostera is growing, for the purpose of ascertaining the uumber of the 

 seedlings, is rather ditticult to effect. 



The different vegetations of Zostera show a great difference in regard to the 

 uumber of the flower-bearing shoots; at some piaces one finds them in quantities, 

 at other piaces one cannot fiud a single specimen for long distances. In all 

 probability the number varies also year by year. 



The flowering begins in June and is continued during the summer, the 

 flower-bearing shoots coustautly producing new infiorescences. On investigating 

 such a shoot in mid-summer infiorescences in all stages of development are there- 

 fore found. I have found the first ripe fruits in the first week of August or there- 

 abouts. The infiorescences which develop last seldom or never have ripe fruit, 

 partly because the fecundation probably fails and partly because the whole fiower- 

 bearing shoot is thrown off or broken later in the autumu, at the time when the 

 large quautity of leaves is thrown off. It is thus seen that the flower-bearing 

 shoots only remain in existence for some months (4 — 5). 



1 am not able to state Avhat is the cause of the abundance of fiowers; I 

 have come across good fruit-bearing shoots in calm fjords on soft bottom as well 

 as in the open Kattegat on hard bottom; nor does the depth seem to be of any 

 consequeuce. 



