465 MISS T. L. PRANKERD ON THE STRUCTURE OF 
elements running parallel with the surface of the seed from the chalaza to 
the mieropyle. Аз far as the integument is confluent with the nucellus, they 
are five or six rows deep, but they thin out in the canopy, and die out a 
little below the apex. In transverse section they are roughly circular in 
outline, or, as they fit closely, somewhat hexagonal by pressure, and measure 
30 u in diameter. In the absence of a truly median longitudinal section, it is 
impossible to get at their real length, and often diffieult to measure the part 
of the fibre included in the plane of the section, but in a favourable instance 
this reached 350 р, and many were probably much longer than this, 
The impression given by most preparations, both transverse and 
longitudinal, is that the fibres were thick-walled, which, on general com- 
parative grounds, one would expect. "There are, however, several different 
types of preservation of this tissue: and, in the absence of those “ critical 
histological investigations . . . . upon fossilized cells and tissues” to which 
Oliver has called attention (14, p. 89), № may be as well to consider them 
in detail. 
(«) We have first what may be termed the ordinary type, where the walls 
are very thick, and only a small lumen is shown, which is sometimes 
obliterated (К. 20а (2) & Pl. 24. fig. 24). In this type narrow spaces are 
often to be seen between the elements, each spaee frequently showing a 
delicate line in the centre. This is probably an effect of mineralization, and 
means that the whole of the thickening layers have contracted away from 
the middle lamella. When the fibres possess no lumina, this is no doubt 
merely due to the greater thickness of the section, which if rubbed down 
further would probably show them. 
(^) A striking contrast is afforded to the foregoing in the preparations 
It. 22 and 28, of which the former is a very beautiful, accurately transverse 
section across the seed near its base (РІ. 24. figs. 27 & 28), and the latter 
an oblique section across the canopy. Here it will be seen that the walls 
of the fibres are comparatively thin, and that the cells occasionally show some 
contents as seen in РІ. 22. fip. 2. 
(c) In a third type of preservation (В. 20 a) the walls appear even thinner, 
but all the cells have thick, dark brown contents (РІ. 22. fig. 1 а). 
(d) Yet a fourth appearance is seen in preparation R. 21а (PI. 22. fig. 1 e), 
where the walls are relatively thin, though very dark and decisive in character, 
the contents appearing almost black and confined to the centre of the cell, 
from which delicate strice radiate. 
Tho above types are fairly well defined, though some specimens show 
transitional characters, and there are many more where the preservation is 
not good enough to exhibit any particular type. 
If we believe, as we surely must, that the above all represent a definite 
histological strueture originally existing, our task is to discover what that 
was, and then to attempt a reconciliation of the varying appearances. 
