OF NORTHUMBERLAND AND DURHAM. 315 



82. SPIRULINA, Turp. 

 1. S. TENUissiMA, Kutz. Hai'v. Man., p. 229. Phyc. Brit., t. 

 105 (C). Atlas, PI. LXXIX., fig. 374. Johnst. 

 and Cr., vol. iv. , p. 193. 

 This also I have not seen, except in the aquarium, where I 

 found it on decaying Algge, chiefly on Phyllopliora Brodkei. It 

 forms one of the most beautiful and interesting of microscopic 

 objects. The filaments appear like very slender screws of a 

 delicate green tint, and their motions are very active — contrast- 

 ing strongly in both respects with the Oscillatoria. — D. 



EXPLANATION OF PLATE XV. 



Laminaria flexicaulis, Le Jolis. 



Fig. 1 Portion of stem. Natural size. 



„ 2 Transverse section of stem. Natural size. 



„ 3 Do. do. Magnified. 



„ 4 Transverse section of frond. Magnified. 



Laminaria Cloustoni, Edmonst. 



Fig. 5 Portion of stem. Natural size. 



„ 6 Transverse section of stem. Natural size. 



„ 7 Root — the processes being broken off near to tlitir origm. 



Half the natural size. 



„ 8 Transverse section of stem. Magnified. 



a. subcortical canals (vasa mucifera). 

 h. central axis (pithj. 

 „ 9 Inner surface of frond, with "msa mucifera.'''' Mag- 

 nified. 



„ 10 Transverse section of frond. Magnified. 



a, a. — " vasa mucifera.''^ 



