MUELLER : OBSERVATIONS ON LAMINARIA BULLATA KJELLM. 305 



lations are most perfect, being more greatly elevated and de- 

 pressed, though not so large in diameter as in portions near the 

 apex. 



The plant is a perennial, and towards the older portion of the 

 lamina the bullations become broader and more shallow until 

 they finally disappear, leaving the older portion of the lamina 

 with an even surface (Jig. /). 



The greater part of the material was preserved in a five per 

 cent, solution of formaline, a little alcoholic material was used. 

 The former proved the more satisfactory. Free hand sections 

 mounted in glycerine jelly were used for study. 



ANATOMY. 



Laminaria bullata, like the other members of the Laminari- 

 aceae consists of three tissues, viz., the epidermal, the cortical, 

 and the pith. Only the first two are found in the hapteres, 

 while the stipe and lamina contain them all. 



The surface of the plant is covered by a thick structureless 

 cuticle ; below this are the epidermal cells, prismatic in form, 

 about one and one-half times as long as broad, but with the 

 two shorter diameters equal, so that when the cells are seen 

 from the surface, they appear as cubes or pentagons. 



These epidermal cells are densely crowded with chromato- 

 phores, their chlorophyll being masked by the brown coloring 

 matter characteristic of the kelps. The outer wall is compara- 

 tively thick while the lateral and inner walls are rather 

 thin. 



Below the single layer of epidermal cells are found from two 

 to four layers of cells which are shorter and broader than the 

 epidermal cells, and not so densely crowded with chloroplasts. 

 These are the hypodermal cells. 



Next to the hypodermal cells are found the cortical cells, 

 which are more irregular in form, though still prismatic. They 

 increase in size towards the center of the plant, and are followed 

 by strengthening cells which are smaller in diameter and longer 

 than the cortical cells. They also have thicker walls and some 

 of them are imbedded in the mucilaginous material of the central 

 part of the plant. These cells are devoid of chromoplasts, but 

 contain granular protoplasm. 



The pith web consists of numerous colorless, interlacing 

 and anastomosing hyphae embedded in mucilage. 



