( 223.) 
XI.—On the Embryogeny of Tropeolum peregrinum (LZ.) and T. speciosum 
(Endl. and Poepp.) By A.EXANDER Dickson, M.D., Edin. & Dublin. 
Regius Professor of Botany in the University of Glasgow. (Plates XIV.— 
XVI.) 
(Read 19th January 1874. Given in for publication 14th May 1875.) 
Introduction. 
The extraordinary processes developed in connection with the base of the 
suspensor in the common Indian Cress (7ropcolum majus) have long excited the 
interest of vegetable embryologists, and have led to the publication of numerous 
observations on the embryogeny of that plant. As the following remarks are 
interesting chiefly in regard to the peculiar features in which the germs in two 
other species of the genus differ from that in the common Indian Cress, it will 
not be out of place for me briefly to recapitulate the principal facts connected 
with the development in that plant. | 
The repeated subdivision of the fertilised germinal vesicle in 7. majus very 
soon results in the formation of a small flask-shaped structure, resembling in 
figure a soda-water bottle, having a short neck, ovoid body, and pointed base 
(Plate XV. fig. 18, A, after Hormeister; Band C after Scuacut). The pointed 
base fits into the correspondingly pointed apex of the embryo-sac. The neck of 
this structure becomes gradually elongated; and by an active cell-multiplication 
at its extremity, a somewhat globular head is produced, which ultimately 
becomes developed as the embryo proper; while the slenderer proximal portion 
constitutes the suspensor, which here is remarkable for consisting of several 
longitudinal rows of cells. - At a very early period the outer side of the body of 
the bottle-shaped germ becomes the seat of active growth, resulting in the for- 
mation at first of a rounded projection, which afterwards increases and elongates 
into a thick cylindrical process, which pushes or bores its way through the 
coats of the seed a little to the outer side of the micropyle, and runs as a long 
_root-like process free in the cavity of the seed-vessel. A little after the first 
appearance of this process a somewhat similar rounded projection appears on 
the inner or ventral aspect of the body of the germ, but a little nearer the basal 
point than the extra-seminal process. This new growth gradually elongates, 
becomes tapering and pointed, insinuating itself as a slender and delicate root- 
like structure through the tissue of the neck (/wniculus) of the seed, and, 
reaching the placental vascular bundle just where it curves outwards to enter 
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