Sporochnoidece.'] desmaeestta. 131 



3. DEs:vrA£ESTiA ACULEATA, Lmiioiir. Spined Besfiiarestia. 



Hab. In the sea. Common. Perennial. 



The root is a hard disc. The frond is without a midrib. 

 From one to three feet long. When young, the branches 

 are beset with distinct pencils of fine green filaments ; when 

 these fall off they are succeeded by stiff spines, so that 

 it appears quite a difl'erent plant. When old, it becomes 

 harsh and woody. " It is scarcely possible to conceive a 

 more beautiful object tlian this plant waving its young and 

 delicately-feathered fronds in the water. ''^ When it has lost 

 its fine green ornamental pencils, the colour is dark olive. 

 Whenever the plants shoot out young branches, they are 

 always clothed with the fine green filaments which, con- 

 stantly accompamdng growth, probably perform the func- 

 tion of leaves. No fructification has yet been observed on 

 any of these three species of Desmarestia. It is mentioned 

 as a remarkable thing of these Sjoorochnoideai, that they 

 change the colour of other Algse when put into the same 

 basin of water with them, and cause^ speedy decomposition 

 when they come in contact with them. 



The branches are at times adorned with delicate parasitical 

 Algse, and still more frequently with TMhulijJora serpens and 

 other zoophytes. On the coast of Ayr the large tufts of it 



