II. Structure and growth of the Zostera. 



If one rows aloug in a boat at low water iu almost calm weather and looks 

 down upon the dark-green vegetation of the grass-wrack, one only catclies sight of 

 the loug ribbon-Hke leaves waving hither and thither with the motion of the water. 

 In summer-time the flower-beariug shoots, which will be described later, are also 

 sometimes visible. In order to investigate the plant more closely a iew shoots 

 may be loosened by means of a rake, an oar or a dredge. It is then seen, that 

 Ihe leaves are placed on a jointed and brittle root-stock, which has been growing 

 iiorizontally creeping in the bottom of the sea, a little below the surface of tlie 

 ground. The leaves are plaoed in two rows, alternately to the right and to the 

 left, and each leaf consists of a lower tubular part, called a sheath, which encloses 

 the younger part of the shoot, and the long flat, rihbon-like blade. The older leaves of 

 a shoot are placed on the root-stock witli a space of 1 — 2 cm. between them, and 

 the piaces where the leaves arise give the latter a nodose appearance, as each 

 sheath forms a projecting ring or ridge. At the base of the sheath two tufts of 

 rather long, branchless, white roots develop, fastening the plant to the bottom. 

 Towards the end of the shoot the internodes of the rootstock are cjuite short 

 and are only seen if one leaf after another is picked off; it is here that the shoot 

 is growing. At some piaces sideshoots are found; there is in reality a small bud 

 in the corner of each leaf, which is the germ of a sideshoot, yet only very few 

 of these will develop. From a botauical point of view the position of the buds 

 is rather peculiar, as they are not placed right down in the axil, i. e. just inside 

 the base of the sheath, but a little higher, just below the base of the next sheath. 

 We have no explanation of this peculiaritj^; it is perhaps because it would be 

 difficult for the small bud to find room inside the base of the sheath. The side- 

 shoots develop into shoots of the same kind as the mother-shoot, and as each of 

 the slioots only consists of some few nodes, the root-stock gradually dying away 

 from behind or easily broken, the side-shoots soon develop into independent bran- 

 ching shoots. It is thus easily understood that in tids way a multitude of shoots 

 are formed which weave together tlie tliick carpet of which tlie Zostera vegeta- 

 tion consists. 



Grass-wrack is green all the year round and luxuriates in the warm and 



