15 351 



bably be forced to turn one of the broad sides of the leaf upwards and thus be 

 able with the greatest possible surface to intercept the rays of light. In this con- 

 nection it is also of interest that Caiilerpa Webhiana f. disticha, the Caulerpa- 

 species I have found deepest down and whose small ca. 1 cm. high and rather 

 rigid leaf can scarcely be bent by the current, has its leaves curved outwards 

 and then downwards with the flat side upwards towards the light just like a 

 dorsiventral leaf. 



(2) The radial Caul er pas. In the Danish West Indies these are represented 

 by the two form-rich species C. racemosa and C. ciipressoides and by C. uerticillata. 

 The last-mentioned species I have already dealt with; in the West Indies it fre- 

 quents the very quiet habitat on the roots of the mangroves where its finely divided, 

 bushy assimilators seem to be well adapted to the surrounding conditions of life. 

 Of Caulerpa racemosa we have the varieties var. iwifera, var. clavifera, var. occi- 

 dentalis and var. lœtevirens, and of Caulerpa ciipressoides var. mamillosa, var. erici- 

 folia (which typically developed has not yet been found in Danish West Indies), 

 var. typica and var. pliimarioides which already has many distichous branches. In 

 what localities do we meet with these forms? If we first consider the forms of 

 C. racemosa, then var. clavifera and var. uvifera are both commonly met with in 

 shallow' water near the surface of the sea. Var. clavifera is so to speak met with 

 everywhere on the coral-reefs or rocks in somewhat exposed places. It grows here 

 in a dense carpet between corals and Lithothamnia, but also on rocks. And often 

 it grows so near the surface of the sea, that at low water it is laid more or less 

 dry. It can grow in rather exposed localities and the more exposed the shorter 

 are the assimilators while the rhizomes grow more intertwined; thus we get the 

 characteristic, compact carpets which upwards are formed by the densely placed 

 ramuli downwards by the rhizomes (cfr. Fig. 25 and 26). When the plant has this 

 form it is fastened immovably to the rocks. If we go to a little more sheltered 

 locality or a little deeper water (one meter or two) we find that the assimilators 

 grow longer; we meet here with forms of var. clavifera, of var. uvifera and of 

 var. occidentalis; the rather long assimilators in these forms wave to and fro in the 

 sea. These three forms are all, as far as I have seen in Danish West India, attached 

 to rocks and coral-reefs, that is, firm bottom. Of the raceniosa-forms I have only 

 found the form I have called var. lœtevirens on loose bottom in shallow water. As 

 I have mentioned it in more detail in the systematic part, this form was found 

 growing in a locality where the water was always unclear; it is therefore to 

 be considered as a shadow-form which comes rather near to the forms from 

 deep water. 



The radial forms of Caulerpa ciipressoides grow in very similar localities as 

 those of Caulerpa racemosa and show quite parallel growth. Var. mamillosa which 

 occurs in the most exposed localities where this species is to be found, is common 

 on and especially inside the coral-reefs where accumulations of coral-sand are 

 found ; at the most exposed places the ramuli are quite short and occur in 6 — 7 



