Johnson . — On A rceuthobium Oxycedri. 151 
fruit by an account of the microscopic structure. In a vertical 
median section of a ripe fruit (Fig. 8) the centre is seen to be 
occupied by ordinary endosperm tissue of large volume and 
with a single median embryo Imbedded in its apical part 
(Fig. 9). I have never found more than one embryo. It Is 
straight, with the two cotyledons only very slightly indicated. 
Its radicle is superior and has no root-cap; the whole embryo 
is covered by a continuous layer of columnar dermatogen- 
cells (Fig. 10); the radicle is exserted ; the endosperm-cells 
extend no further upwards than to the point at which the 
hypocotyledonary stem passes into the radicle. The protective 
function of the root-cap is apparently assumed by the apical 
part of the ovarian papilla which forms a conical cap of empty 
cells covering the radicle much as the calyptra of the Moss 
covers the tip of the developing sporogonium. The absence of 
a true root-cap and the faint indication of the cotyledons 
are characters in keeping with the parasitic habits of the 
plant, and are conspicuous in other parasites, e. g. Cuscuta 1 . 
The only differentiated part of the embryo is the epidermis ; 
the sub-epidermal tissue is uniform,, and there are no pro- 
cambial strands. 
Owing to the absence of the integument of the ovule, 
and consequently of the testa of the seed, the protective 
function of the testa is assumed by the endocarp, which 
forms a complete envelope to the seed when the latter 
is forcibly ejected from the dehisced fruit. The endocarp 
consists of some five layers of cells. All the layers 
except one, and this the outermost, consist of simple 
thick-walled cells without contents, parenchymatous at 
the apex and base, prosenchymatous laterally. The outer- 
most layer is, except in its basal part, converted Into obliquely 
radiating viscid cells, some of which are half the length of the 
seed proper, their length as a general rule being greater the 
nearer they are to the radicular end of the seed. The walls of 
1 Goebel, Vergl. Entwick. d. Pflanz. ; Anhang, Parasiten, in Schenk’s Hand- 
buch der Botanik, 1884, p. 374. 
