of Bennettites gibsonianus , Carr. 443 
the hard middle layer of the testa a small gap a , towards which 
the vascular bundle of the seed- stalk advances from below. 
Inside the hard layer is a small flat expansion of compact 
tissue, produced, as the surface-view shows, by the divergence 
from one another of the tracheal elements of the vascular 
bundle which terminates here (see PI. XXV, Fig. 3). On 
this point there can be no doubt ; we have here the behaviour 
which we so often find in the chalaza of gyrnnospermous 
ovules. If the testa is separated from the nucellus in breaking 
open the fructification, as sometimes happens, and the nucellus 
of the seed is exposed (PL XXV, Fig. 6 ), it shows, at the spot 
where the chalaza expands, a small impression from which a 
number of shallow furrows radiate towards the apex. 
The most difficult part to understand in the whole of the 
seed is the tubular prolongation of the testa beyond the apex 
of the nucellus. It is far from being so simple as it appears in 
Carruthers’ drawing \ and my own diagrammatic delineation 
is probably not quite correct, even if it comes on the whole 
near the actual condition. There are difficulties in the way of 
investigation which are quite insuperable with such scanty 
material. First of all the peculiar position of the seeds in the 
spadix makes it impossible to secure the necessary exactness 
in the direction of the sections. We can follow the general 
direction, but beyond this we are dependent on chance. 
Further, the upper extremity of the seed is so extremely 
slender that the slightest deviation from the median line at 
once produces oblique sections. Then the periphery of the 
spadix, which in this case is the important part, is usually 
particularly rich in pyrites, and this drops out when the slices 
are reduced to the needful thinness. Under these circum- 
stances, to obtain an exactly median longitudinal section in 
serviceable preservation is a piece of pure good luck, which 
has never fallen to my lot. The pyrites is also particularly 
embarrassing in the case of preparations which are tangential 
to the surface of the spadix, and in which we get a more or 
less exact transverse section of the apex of the seed ; more- 
1 Carruthers, loc. cit, pi. 59, f. 6. 
