OF THE RAPHE IN SEEDS. 107 
hilum, near the bottom of the ventral margin of the nut, and at last arriving at the basal 
point, it terminates abruptly by penetrating the integuments: between this point and the 
hilum a very short space intervenes, which is obsoletely angular, and immediately at this 
angle, close to the margin, the small embryo is found imbedded in a large albumen, the 
radicle pointing outwards, and the two short fleshy cotyledons, greatly divaricated, being 
directed towards the vertex of the seed. Here then, as far as regards its direction with 
the hilum, the embryo is anatropal, having become inverted half a turn on its centre from 
its normal position, while the integuments have performed an entire gyration, by which 
the embryo is deprived of its anatropal characteristic. All the species of Mollinedia 
which I have examined have regular anatropal seeds, with one exception, where the 
raphe is cyclotropal, as in Citrosma. We have thus in Citrosma a verification of the 
fact observed in Stemonurus, the raphe terminating at a point exactly contiguous and 
corresponding to the radicle of the embryo, a fact quite incompatible with the laws of 
structure so beautifully expounded by Mirbel: it is a development that has hitherto been 
considered impossible; but I will proceed to show that these are not the only instances 
of the same occurrence we find in the structure of seeds. 
In the development of the seed of the Queurbitaceæ, we meet with a structure that 
offers much resemblance to the anomalies observed in Stemonurus; we find also other 
features, not only difficult of explanation, but contrary to all our ideas of the nature and 
function of the raphe. To aid us in the solution of these phænomena, we will first recur 
to the detailed account of. the development and growth of the ovule of Queumis Anguria, 
L., from the observations of Mirbel (Mém. Acad. Sci. Paris, ix. 621. tab. 1). The 
growth of the anatropal ovule is here shown in all its earlier stages, and we see that by 
the time of the fall of the flower, the micropyle of the primine and secundine becomes 
quite closed over the tereine; soon after which, a fine thread is observed to grow out of 
the micropyle, which was first noticed and described by Brongniart, in the ovule of Pepo 
macrocarpus and Momordica Elaterium. As the growth of the ovule proceeds, this 
tubular thread becomes covered by an envelope formed of cellular tissue: according to 
the drawing of Mirbel (Joc. cit. tab. 1. fig. 10), it is a prolongation of the mouth of the 
embryo-sac; but Griffith says (Posth. Notes, 153), that although he had observed the 
same fact in several instances in Cucurbitacee and Asclepiadaceæ, he was never able to 
trace any connexion with it and the embryo-sac, and was rather disposed to consider this 
thread as formed by the boyaux or pollen-tubes, an opinion confirmed by the observations 
of Schleiden, and which appears the more probable conclusion, as no remainder of this 
thread is visible in the ripe seed. At the period above mentioned, the bottom of the 
embryo-sac breaks away from the gangylode, becoming thus suspended by its — and 
the embryo is formed in its summit: there is no appearance 1n the raphe at this time to 
indicate any other change than the ordinary anatropal development. The same course of 
TE i i ir generally among the Cucurbitaceæ. We will 
metamorphosis is said by Mirbel to occur ge y ng ppt 
now compare these changes with the development found in the ripe "m d z = 
analysis of Citrullus Colocynthis as a fair example of the structure ot the ur 
family. 
Here the seed is obovate, much compressed, its hilum being an open slit along its 
P 
