The Causes of the Zoning of Brown Scaxeeccls. 201 
this means a rough imitation of the periodic exposure by the tides 
was obtained. The plants were treated in this way for twenty- 
four days, and even in this comparatively short period they showed 
marked differences according to the conditions. Text-figs. 28—30 
show the effects on the growth of the different species. 
ZONING o r SE AWEEDS 
Young ' seawegos g no wn ? . -peeks' 
IN I HR, _■ oily -is f\S ■ 
FOCUS \SERkATVS 
specimens all ths t> 
\ . . . 
FOCUS VE&iQ U.L.C-SV? .. 
sumtmm m 7 spl-ciheUS ■ 
■M 
ASCOPHYkLim 
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Fucus 
Fig. 30. In water 1 hour ; dry 11 hours, x §. Fucus serratus died in a 
few days. Fucus vesiculosus grew very little, and became shrivelled at the base. 
A scophy llum nodosum : growth very stunted. Fucus ceranoides ; grew slowly; no 
specimen died. 
The specimens of Fucus serratus died in two or three days in 
jar C. In jar B most of the plants flagged in ten to fifteen days, 
but one was was still alive at the end of the experiment. In jar A 
they grew very quickly, and after the first six or seven days were 
far ahead of the other seaweeds in the jar; but after this they 
flagged and one or two of the specimens finally died. 
