272 CUNJUGATIONS OF DIATOME®. 
at least peculiar. 1st. The oblong plan of calyx. 2nd. The oblong 
plan of petals the reverse way to calyx. 3rd. Two sepals of the calyx 
higher on the stem than the other two; and 4th. The curious recep- 
tacle on which the smaller stamens grow. They can all be easily 
explained in the following manner :— 
Ist. As the single stamens are further removed from the ovary than 
the two pairs are, room must necessarily be made for the bases of these 
two stamens (z,E, Fig. 1), hence the oblong plan of calyx this way. 
2nd. For the same reason, viz. that these stamens are so far from 
the ovary, they push between the pairs of petals and elongate the petal- 
plan the other way. 
8rd. One pair of sepals are higher on the stem than the other pair, 
because the two odd stamens form a second whorl, that are lower on 
the receptacle than the pairs, therefore these two odd stamens push 
down two sepals (m,M, Fig. 4). 
4th. The curious receptacle of the odd stamens (x, Fig. 4). In 
Megacarpea polyandra, there is a receptacle all round the bases of 
the stamens. Therefore I suppose normally in all Crucifere there is 
a receptacle at the base of the second whorl, but as the second whorl of 
stamens is incomplete in nearly all the Cruciferae, the receptacle is in- 
complete also. J look therefore upon these appendages at the bases of 
the odd stamens as imperfect remains of a receptacle that should go 
all round, but is partially suppressed, in the same manner as the sta- 
mens of the second whorl are suppressed. 
CONJUGATIONS OF DIATOMER. 
SAY LI Carter, F.R.S. 
During the first half of the last month (July, 1864), T have found 
three species of Diatomee in conjugation, viz. Navicula serians, Ktz., 
N. rhomboides, Ehrenb., and Pinnularia gibda, Ehrenb., all in heath-bog 
water in the neighbourhood of Budleigh-Salterton, on tbe south coast 
of Devonshire. All conjugate after the manner detailed and illustrated 
long since by others as well as myself, but here there are besides spo- 
rangeal frustule-cases, and these are ringed as first described by Dr. 
Griffith, and also rightly inferred by this naturalist to be siliceous, be- 
cause they do noć dissolve in nitric acid, 
