Apr. IS. 1915 



Organic Constituents of Kelps 



41 



on the analytical samples collected by Mr. Guy R. Stewart, of this labora- 

 tory. Every precaution was taken to insure fair and representative 

 samples, as described in the preceding paper (32). Tabulations are 

 made on the water-free basis and also on the original material. In the 

 consideration of possible utilization of kelp products proper emphasis 

 should be given to the high percentage of water in the plant. 



A qualitative examination of the varieties of kelp investigated indi- 

 cates the presence of very complex compounds in a highly colloidal state. 

 Starch and soluble reducing sugars are absent from these plants. In all 

 cases strong tests for furfural (pentosan test) are given, and some samples 

 gave the galactan test by oxidation with nitric acid. The major portion 

 of the total organic matter present is insoluble in water and in alcohol. 

 These relations are given in Table I. 



Table I. — Organic matter in kelp 



No. of 

 sam- 

 ple. 



42 



43 



44 



45-1 



45-2 



46. I 



46. 2 



47. I 

 47.2 



Species of kelp and part used. 



Egregia spp 



Laminaria andersonii 



Iridaea sp 



Nereocystis luetkeana, leaves 

 Nereocystis luetkeana, stems. 

 Macrocystis pyrifera, leaves. 

 Macrocystis pyrif era, stems. . 

 Pelagophycus porra, leaves. 

 Pelagophycus porra, stems. . 



Percent- 

 age of 

 total 

 organic 

 matter 



67.87 

 73.80 

 69. 12 

 47.27 

 39.02 



54-3° 

 51. 22 

 58.60 

 37-35 



Percentage of plant. 



Water- 

 soluble 

 organic 

 matter. 



10. 08 



23-32 

 25. 80 

 18.88 



13-24 



11. 56 

 25.40 

 23-32 

 14. 40 



Alcohol- 

 soluble 

 organic 

 matter. 



6.84 

 8. 56 



8. 16 



12. 72 

 6.68 

 8.36 



13. 12 

 18. 04 



9. 28 



Percentage of total 

 organic matter. 



Water- 

 soluble 

 organic 

 matter. 



14.9 

 31. 6 



37' 

 39 

 Z2, 

 21, 



49 



39-8 



38-5 



Alcohol- 

 soluble 

 organic 

 matter. 



10. I 



11. 6 

 II. 8 

 26. 9 

 17. I 



15-4 

 25. 6 

 30.8 

 24.9 



It may be noted in this connection that certain varieties of marine 

 algae, investigated in other parts of the world, have shown different 

 chemical characteristics. Levulose, mannit, starch, and easily hydro- 

 lyzable polysaccharids have been reported (2, 18). 



Table II gives the general composition of the various portions of the 

 kelp plants for the different species investigated. The extent of the 

 variations between individual plants is indicated in Table III. The 

 total organic matter varies from one-third to three-fourths of the dry 

 weight. Using the conventional factor of 6.25 for nitrogen, we have as 

 high as 17 per cent of protein if all the nitrogen existed in that form. 

 (The forms of nitrogen will be discussed later.) The plants of Macro- 

 cystis obtained at Pacific Grove are distinctly higher in this constituent, 

 as compared with the samples of Macrocystis from the vicinity of San 

 Diego. In none of the species is the percentage of ether extract important, 

 the average exceeding i per cent in only the one case of Nereocystis 

 79827°— 15 4 



