constituents like fucosterol and the algal terpenes which are at present being investigated. Russel-Wells has shown that the fats increase with depth of emergence from 0.16% in L. digifata to 3.6% in Pelvefia canaliculata. Work in progress indicates that fucoidin also increases with depth of emergence. The possibility of the presence of perhaps valuable constituents has yet to be explored.
Srmrnrary of rezctlfs
The ash, iodine, crude protein, mannitol, laminarin and alginic acid contents of samples of F. serrafru, F. vesinrlosrrs, F. spiralis and Pelveria cmalicrilata taken at monthly intervals from April, 1945, to March, 1947, have been determined.
The chemical composition has been correlated with the depth of immersion of the weed. In general, on the anhydrous basis, the ash, mannitol, laminarin and iodine contents decrease with depth of emergence. The Fucaceae show a very regular seasonal variation, the graphs for the dry weight, mannitol, laminarin and ash all show two maxima and two minima in each year. The figures indicate that the rate of photosynthesis increases earlier in the year in the littoral zone as compared with the sub-littoral zone.
The'graphs giving the seasonal variation in the crude proteins are almost identical for the four species, and similar to those for the Laminariaceae. They do not appear to bear much relationship to the metabolism of the plant but can bc correlated with the inorganic nitrate in the seawater.
The theory of isotonic substitution which applies to the Laminariaceae cannot be applied to the Fucaceae which appear to have a different metabolism.
The decrease in mannitol, laminarin, ash and dry weight content in July of each year is significant, and possible explanations have been advanced.