17 353 



fronde du C. proliféra qu'on i)rendiait les deux formes, vues séparemment, pour 

 des plantes distinctes". But when we know this we have good reason to suppose 

 that other Caulerpas will also show themselves to be highly changeable under 

 altered external conditions of life and therefore that many variations may arise 

 from this variability. 



When we e. g. find in Caulerpa cupressoides that the number of rows of 

 branchlets (pinnules) decrease as we go from exposed coasts with shallow water to 

 sheltered localities and especially to deep water, and when we find a similar ten- 

 dency in other species e. g. C. racemosa under similar conditions and when we 

 further know that we have the radial species in shallow water and chiefly the 

 bilateral species in deeper water, then I think this decrease in the rows of branch- 

 lets goes to show an ecological adaptation, and it is therefore quite natural that 

 we should often find in the same plant a ditferent number of rows of branchlets, 

 as is indeed often the case in localities which might be considered as intermediate. 

 Thus e. g. in the lagoons, which can be considered as intermediate localities 

 between exposed coasts and deep water, we meet with forms of C. cupressoides 

 which are Ijust characterized by having a varying number of rows of pinnules. 

 Also the form itself of the pinnules is certainlj' highly dependent on the external 

 conditions. On exposed coasts these are commonly short and broad, on sheltered 

 coasts longer and more cylindrical, which is clearly expressed in the two form-rich 

 species C. racemosa and cupressoides. 



The conclusions I have thus reached arise solely from studies in nature, but 

 when one has seen there how often quite small variations are immediately reflected 

 in the individuals in such a way that they are steadily altered in a fixed direction, 

 there must be good reason for believing that by experimental cultures we may 

 reach to similar results. For the rest I believe that by exhaustive examination 

 of nature itself we may yet obtain very much. When Svedelius in mentioning 

 a dwarf-form, forma interrupta of C. taxifolia, thus writes (1. c. p. 100): "in which 

 stunting has perhaps been produced by lack of light, owing to the great depth, for 

 Caulerpa, at which it grows (more than 10 m.)", then the poor development of 

 this form can scarcely be ascribed to a "great depth" as Svedelius thinks, since I 

 have found in nearly three times the depth large and well-developed specimens of 

 Caulerpa taxifolia (cfr. fig. 10) just as in still greater depths (about 40 — 50 m.) I have 

 found well developed specimens of other species. When Svedelius repeatedly calls 

 10 m. a great depth it only shows that he has not succeeded in dredging in greater 

 depths, which as I know from experience is often difficult in the tropics. I have 

 as mentioned above succeeded in getting sea-weeds in about 50 meters depth, but 

 I am quite sure as already pointed out (6, page 769) that a fixed algal vegetation 

 maj' be found in twice the depth and perhaps more in tlie tropics. 



And when Svedelius regarding C. proliféra writes p. 83 (cfr. also p. 88) : 

 "(It) is in the Mediterranean apparently a pronounced still-water form, which even 



1). K. n. Videiisk Selsk. Skr., 7. Rrekke, nalurviilensk. o(! nuilhein. Afd. IV. 5. 46 



