Triglochin maritimum , L. 97 
perianth whorl will be spoken of as the sepals, and the 
individual parts of the inner ring as the petals. 
The individual whorls arise in acropetal succession from 
the first primordium. 
Calyx . The anterior sepal arises first; it takes its origin 
from the basal part of the spherical primordium already 
referred to. The shape of this young sepal is somewhat 
crescentic, and of a fair thickness. Very soon after the first 
sepal has made its appearance the two lateral sepals arise, 
the left-hand one originating slightly before its fellow on 
the right-hand side (Figs. 15-18). 
Corolla. After the sepals have grown slightly the petals 
commence to put in an appearance. They arise in positions 
alternate with those of the sepals, the posterior petal origi¬ 
nating first; it does so as a small rounded outgrowth, which 
is more or less flattened. The shape of these young petals 
is not nearly so elongated as that of the young sepals; they 
are also very much smaller, and arise in a position situated 
higher up upon the original primordium. The other petals 
follow very quickly—indeed almost simultaneously—so that 
it is somewhat difficult to say which of the two lateral petals 
develops first: as far as can be made out, the petal which 
occupies a position between sepals 1 and 2 is the first to 
appear, and is very quickly followed by the other. It some¬ 
times happens, however, that the first lateral petal to arise 
is that lying between sepals 1 and 3, so that a certain amount 
of variation may occur (Figs. 19 and 20). 
The Androecium . As soon as the segments of the perianth 
have become differentiated, the stamens make their ap¬ 
pearance. 
The outer staminal ring, as already pointed out, is opposite 
the outer perianth whorl (sepals), and it arises before the 
inner ring of stamens as oval-shaped masses of tissue (Fig. 21). 
It seems very probable that the appearance of each stamen 
follows that of the perianth segment to which it is opposite, 
for it was observed that the stamen superposed on the first 
sepal was the first to originate. It was not seen which of the 
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