HOW TO KNOW THE SEAWEEDS 



104a Main axes here and there much inflated to form the float blad- 

 ders. Fig. 139 Ascophyllum nodosum 



Fig. 139. Ascophyllum nodosum (Linnaeus) Le Jolis 



An upper portion of a fertile plant showing hol- 

 low vesicles in the main axes and the stalked, club- 

 shaped, deciduous, receptacular branchlets, X 0.6. 

 A common plant on rocks along the Atlantic Coast 

 to the north of New Jersey. 



104b Not as above; vesicles free, individually sti- 

 pitate 105 



Figure 139 



105a Vesicles large, each bearing an expanded 

 blade. Fig. 140 Macrocystis 



Fig. 140. Macrocystis pyrifera (Linnaeus) C. Agardh 



A. Habit of a sporophyte plant growing in posi- 

 tion, X 0.02. B. A blade with its basal pneumato- 

 cyst, X 0.5. This species grows along our entire 

 Pacific Coast, forming great "kelp beds" which 

 in southern California are so richly developed that 

 commercial exploitation is carried out on a large 

 scale for the production of the valuable phyco- 



colloid aigin and its derivatives. Harvesting is accomplished by cut- 

 ting the floating parts of the kelp a few feet below the surface with 

 a large mowing machine installed on a barge upon which the cut 

 kelp is piled for transport to the factory. 



Algin is an amazingly versatile, hydrophilic colloid which has re- 

 cently found numerous uses in industry. Large quantities are used in 

 stabiHzing ice cream, chocolate milk, syrups, icings, puddings, sauces, 

 salad dressings, etc. As emulsifying, stabiHzing and suspending agents 

 algin products serve in the manufacture of a great variety of products 

 such as tooth paste, lotions, pharmaceutical jelly, film em.ulsions, textile 

 sizings, paints, boiler compounds, brazing pastes, polishes, insecticides, 

 oil well drilling muds, battery plate separators, etc. 



One other species, M. integrifolia Bory, distinguished by a flat- 

 tening of the holdfast parts, is present from central California north- 

 ward. 



108 



