704 



beautifully iridescent, as they ar^ able to reflect certain rays of the 

 liglit that readies them, and it lias been proved by an experiment 

 made by Bert hold (1. c. p. 419), that a vigorously iridizing specimen 

 of Chylocladia kaliformis lost its iridizing power by being placed in 

 the shade, and recovered it by being once more exposed to the 

 light. A rich profusion of hairs is likewise probably of some im- 

 portance to the algae, as a means of protection from the intensity 

 of the light. Several of the algae growing in shallow water, especi- 

 ally in sheltered places, e. g. most of the species belonging to the 

 S/zc/f/oszp/ion-association, are rich in hairs. It is however most 

 probable, that the hairs are in the fn^st instance meant to serve as 

 organs of absorption and respiration, as pointed out by Rosen- 

 vinge^. Whether they are likewise capable of defending the algae 

 against the dashing of the waves, as suggested by Henckel (Scripta 

 botanica XX, p. 105), I cannot tell. 



From what precedes it will be seen that I do not fully agree 

 with Simmons when he writes (p. 262): »Was den Einfluss der 

 Lichtintensitat betrifft, so bin ich geneigt anzunehmen, dass man 

 besonders, vas die Florideen angeht, derselben zu grosse Bedeu- 

 tung hat zutheilen wollen. Wie will man namlich erklaren, dass 

 im nordwestlichen Norwegen, wo docli im Sommer nicht von ge- 

 ringer Lichtintensitat die Rede sein kann, die noch dazu wahrend der 

 Ebbe trocken liegende Litoralregion so viele Florideen belierbergt?« 



There are always some Floridece which require a great deal 

 of light, and in the Faeroes, where the light is far from strong, 

 and the direct insolation particularly slight, a great many Floridece 

 may therefore easily thrive on the beach, even above the highest 

 water mark, without fading, whilst they fade in districts with 

 more light, are less numerous, and do not grow so far above the 

 level of the sea, except where local circumstances are especially 

 favourable. 



During a journey in Norway in 1904, I stayed a few days 

 at Christianssund, thus getting an opportunity of observing the 

 algae-flora there. It was interesting to observe, how much less de- 

 veloped the littoral algae-vegetation was here than on the Faeroes, 

 the floral composition of the two vegetations, however, being much 

 the same. The Floridece were faded, light yellow to yellowish- 



^ Rosenvinge, L. Kolderup: Sur Ics organes piliformes des Rhodomelacees 

 (Oversigt over det kgl. danske Videnskabernes Selskabs Forhandlinger, 1903, Nr. 4, 

 p. 447—449). 



