44 HALF AN HOUR WITH SEAWEEDS. 



herbarium, but it remains a pretty object neverthe- 

 less. In the little rock-pools you will notice the 

 sides frequently covered with a red, limy incrus- 

 tation. This is the base of the coralline seaweed 

 (Corallina officinalis, Fig. 12), a little plant of great 

 Fig. 12. interest, and long believed to belong to 

 the animal kingdom, on account of the 

 quantity of carbonate of lime it secretes. 

 It soon bleaches, and then assumes a tint 

 of dirty whiteness. Other algae are now 

 known which have the same power of 

 secreting lime, among which are the 

 genera Jania, Acetabularia, Liagora, and 

 Melobesia. Perhaps one of the most 

 beautiful of the Bhodosperms is the 

 offi- Delesseria sanguined, whose specific name 

 ld sO- greatly assists in its identification. Its 

 colour is of the most beautiful scarlet, and you 

 may further learn to distinguish it by its mid- 

 rib and distinct nervures. Few objects look better 

 in the herbarium, as it dries well without losing 

 its colour, and its mucus acts as a natural gum 

 and causes it to adhere firmly. The Ptilota 

 plumosa is another beautiful red seaweed, whose 

 feather-like fronds will assist you in identifying it. 

 The stiffer, bristle-like fronds of Griffithsia setacea 

 are worth notice, and you will hardly fail to find it 

 growing in the darker crannies of the rock-pools. 

 When a newly-gathered specimen is placed in fresh 

 water, the membrane bursts, and the red colouring - 



