SIR J. LUBBOCK —PHYTOBIOLOGICAL OBSERVATIONS. 79 
white, embedded in the perisperm, and a little shorter than the 
seed. The cotyledons are narrowly oblong or linear, obtuse, 
plano-convex, closely applied face to face, and with their edges 
to the placenta. The radicle is narrower than the cotyledons, 
` inferior, and tapering downwards. 
In P. Coronopus the capsule is many-seeded. The seeds are 
oblong-oval, suddenly tapering to an obtuse point at the lower 
end, small, in transverse section somewhat diamond-shaped, with 
the angles rounded off, and attached to the placenta considerably 
below the middle. They are much smaller than those of P. media, 
and differ much among themselves. The embryo is comparatively 
large, straight, central, nearly equalling the perisperm in length ; 
the cotyledons are linear obtuse, entire, plano-convex, thick, 
closely applied face to face, and with their edges to the placenta. 
In P. maritima the fruit is narrowly ovoid, 2-celled, 2-seeded. 
The seed oblong-lanceolate, biconvex or flattened on the ventral 
side. The embryo is straight, large, and nearly fills the seed ; 
the cotyledons have their edges to the placenta. 
In P. Cynops the fruit is green, with a pale line where the two 
carpels come together, and a darker one along the middle of the 
carpel, giving it in a young state the appearance of consisting of 
four earpels, 2-celled, 2-seeded. The seed is ovate obtuse, pel- 
tate, compressed dorsally, concave on the ventral side, smooth, 
shining, deep green when young, and sufficiently transparent to 
show the embryo by transmitted light. The embryo is straight ; 
the cotyledons linear, obtuse, entire, closely applied face to 
face, with their edges to the placenta. l 
In P. arenaria and P. major the cotyledons are also placed with 
their edges to the placenta. , 
I was for some time much puzzled as to why the cotyledons in 
P. media should be placed differently from the other species exa- 
mined ; though the reason seems in reality very simple. At first I 
thought it might have reference to the mode in which the embryo 
emerges from the seed ; but this does not seem to have any bearing 
on it. InP lanceolata, however, and its allies the cotyledons are 
narrow and thick ; and the seed being somewhat compressed, it 
Will be seen from fig. 163 that if the embryo had been placed 
with its faces to the placenta, it would not have had room to 
develop itself. . 
On the other hand, in P. media the reverse is the case: the 
cotyledons are thin and comparatively wide; their ye in fact, 
H 
