~~ a ee, 
—— me 
~~ P 
POTASH FROM KELP. 21 
Because of the large size attained by Macrocystis pyrifera and the 
difficulty of meeting the environmental requirements, it has not been 
found possible to grow it in aquaria. 
TEMPERATURE. 
One of the most influential factors in distribution seems to be the 
temperature of the water. Kelps grow best in cool or cold water and 
are not found at all in tropical seas. Setchell states that no kelps 
grow on the western coast of North America in water having a tem- 
perature of more than 25° C. The waters along the mainland from 
Santa Barbara to San Diego have an annual range from 12° to 23° 
C. (McEwen, 4); the outlying islands, especially San Nicolas, are 
surrounded by somewhat cooler water. This variation in tempera- 
ture is not too great for Macrocystis, which, according to Setchell 
(7), has a total temperature range of 10° to 25° C. The rate of 
growth is influenced negatively by the temperature of the water. 
' (Cf. Tables 1 and 2 on yields and temperatures, respectively, and 
27 
Temperature 
of the Water 13.45 } 
| in Degrees C. 
‘(Gs 
3) 20.65 
Fic. 12.—Infiuence of temperature on yields of kelp, 1916, 1917, and 1918. The small 
ESTES 3 pe to yields of wet kelp in hundreds of tons per square mile of area 
arvested. ; 
diagrams, fig. 11, showing seasonal variation in yields, and fig. 12, 
showing variation in yield with temperature, for the years 1916, 1917, 
and 1918.) 
TaBLe 1.—Comparative harvests of kelp for the years 1916 to 1920, inclusive. 
January. February. 
No. of bed. © || 
1916 | 1917 1918 1919 | 1920 | 1916 1917 1918 1919 
eeerena eee ices Sar) Seba ee eh ds be CO Ae eee eset by 
SS ee eae eins ig Zeke ies | CTS ncn PE ype Dees + 295 fo eee 
Sy Se ee eee! tA Pe ORs 44,798. foi: pepe de Ard machen 2G So0-T* Saat eee 
SSS eee 4,960 | 14,726 }........ Part oe hes DE 1 W53"|- 5, ete EE. 
SS rrr 2 2S See it. eee | a Te aaa LORS 2 enn Betis S79 o> See 
ae Ee eS ee ce gy nate) ele tats ele pete Ate eed epee tet pice > Peer a = 
ae! aes ee ae. rpecrer Sl oe en ee Noe 13 ee PaRLss 
SE SE ee! 5 Aes aS | Se Ee) IRS me a el aes apie eee 
See eee ce BTR Soap AS RE TOES SCL ES Aer i BEES SIR Ie es 
ea Sa ine aie aire aes oi Tie. 5 ae ahead i ae a 40 106 
_ SES aE es ee 386 TS +=. Cages Te ES Mae hae 200 162 
Ea er ea Hee 2! Rete (OR Lie pm AE aT 9 Cen eo Pe Le Nes ae 328 726 
LSE SESS BE es Dae eee Pe Btn toe gme ce | [OR eg 
_ SS ae Deets Rye Tess 465 190 | Pewter > See See 640 95 676 
vst 8 eee pets ibe: Baes Rake EN silage [) sg ee apis bie ase elie Bilbo ea BT) 50 |.1cs- eee 
\ Ses ee eR ee ee See Pee ee bre PEE Sel ae eS Stace gat culadameaes 100 
4) Sse Vi 24a) Se Bes Oe 72 WEBER! ADD Rk OE ag oe 5D [uso 
_ 5 ee ARE AS 7) SERS 2S 2 2 Ss a Ss a RR Og ER 
ee eee Tes Oe eee aig eae, ES CES See ee Bees eS 
i | 1,424 | 37,100 43,118 | 1,150} 2,136 3,310 | 23,733 24,429 953 1,770 
} | ' 
