No. 422.] PHYLLOSPADIX AS A BEACH-BUILDER 105 
Perhaps the exposure, and consequent partial drying of the 
seed, at low tide helps to crack the testa. At any rate, when 
germination begins the basal end (2) of the hypocotyl bursts 
through the testa and presses the broken edge of it back, leav- 
ing a clear passage for the cotyledon. The 
hypocotyl grows no farther than this, and 
eventually, when its store of substance has 
served to give the young plant a start, it 
dies away. 
The cotyledon grows out little beyond 
the hypocotyl, and is quickly outstripped by 
the ensheathed plumule, which turns upward 
and shortly unfolds to the waves several 
grass-like leaves (Fig. 6). Henceforth it is 
these leaves only which grow upward ; for, 
except for the slender peduncle which bears 
the inflorescence, the only stem of the 
mature Phyllospadix is a creeping root- 
stock, or rhizome. 
Our seedling (Fig. 6) has now quite a start in life, and yet 
it has no root. Its leaves, meanwhile, whipped back and forth 
by the waves, are gradually beaten to shreds, and replaced by 
others. In this way several of the first leaves may 
have lived and died before any root appears. At last, 
when roots are put forth, there are two of them pro- 
duced, not from the hypocotyl, as we might expect, but 
from the stem above the cotyledon (7, Fig. 7). 
That is to say, these are, in the technical 
sense, adventitious roots. When full grown 
. the roots are about two centimeters long, 
stout, and unbranched. . This first pair hang 
Fic. 7. — Young seedling down, one on either side of the stem, and 
with coats removed. c, in- d : 
sertion and of are soon followed by several more which 

Fic, 6. — Seedling with first 
leaves. 



cotyledon ; Z, second node i 
with remnant of leaf; », grow out from the second internode. 
oe When the roots are several millimeters 
long they begin to produce, near their tips, a dense, woolly 
covering of root-hairs, and when a root comes in contact with 
any object, — be it the stem of the Amphiroa (Fig. 8), the rock 
