In describing the form or various external portions of any seed, the hilurri is always to be considered 
as the base. When the seed is quite ripe, the communication through this channel is interrupted: 
it separates from the parent channel without injury, a scar being formed on each. Yet the hilwn is 
so far capable of resuming its former nature, that the juices of the earth are imbibed through it 
previous to germination. 
There are various accessory parts, or appendages, to seeds, which come under the following 
denominations. 
Pellicula, the pellicle, called by Gartner epidermis, closely adheres to the outside of some seeds, 
so as to conceal the proper colour and surface of their skin, and is either membranous, and often 
downy, as in Convolvulus , or mucilaginous, not perceptible till the seed is moistened, as in Salvia 
verbenaca, Engl. Bot. t. 154 . Perhaps the covering of the seed in Chenopodium , called by Gaertner 
Utriculus, is merely a Pellicula. 
Arillus, the tunic, is either a complete or partial covering of a seed, fixed to its base only, and 
more or less loosely or closely enveloping its other parts. Of this nature is the puipy orange-coloured 
coat in Euonymus, t. 302 , the beautiful scarlet cup in Afzelia, and the double membranous coat in 
Hippophae, t. 425 , which last invests the seed within the pulp of the berry. The outer of these coats 
only is described by Gaertner as a peculiar membrane lining the cell of the berry; his “ integumentum 
duplex ” refers to the testa, which I mention only to prevent misapprehension. The Mace, which 
envelopes the Nutmeg, is a partial Arillus, beautifully drawn in Gaertner, t. 41 . Narthecium, Engl. 
Bot. t. 535 , has a complete membranous tunic, elongated beyond the seed at each end, as in many of 
the Orchis tribe; and such seeds, acquiring thence a light and chaffy appearance, have been deno¬ 
minated scobiformia, whence Bergius was perhaps led, very unscientifically, to call the seeds of Ferns 
literally scobs or sawdust! An elastic pouch-like arillus, serving to project the seeds with consi¬ 
derable force, occurs in Oxalis, t. 762 and 1726. In the natural order of Rutacece the same part, 
shaped also like a pouch lining each cell of the capsule, is very rigid or horny; see Dictamnus albus y 
or Fraxinclla, Gartner, t. 69, and Boronia, Tracts on Nat. Hist. t. 4 —7. Besides this coincidence, 
there are many common points of affinity between these plants and Oxalis, concerning colour, 
flavour, habit, and structure. Fagonia and its allies form the connecting link between them, which 
Gaertner and Jussieu did not overlook. We have pointed out this affinity in English Botany, p. 762, 
and it is confirmed by the curious circumstance of Jaquin’s Oxalis rostrata, Oxal. t. 22, having the 
very appendages to its filaments which make a peculiar part of the character of Boronia. 
It is not easy to say whether the various, and frequently elaborate, coat of the seed among the 
rough-leaved plants, Borago, Anchusa, Lithosperrnum, Cynoglossum, Engl. Bot. t. 921, &c. should 
be esteemed an arillus or a testa ; but the latter seems most correct, each seed having only a simple 
and very thin membranous internal skin besides. Gaertner therefore justly uses the term Nut for the 
seeds in question. The same may be observed of Ranunculus , Myosurus , see Engl. Bot. t. 435, 
Clematis, Anemone, &c. whose external coats are no less various and elaborate; yet such seeds are 
as truly naked as those of the Didynamia class, figured in Gaertner, t. 66, each having a double 
skin and no more, which is one covering less than even the genuine nut of the stone fruit, or of the 
Corylas. In Geranium, Malva, &c. what has often been called arillus, is rather a kind of capsule, 
not only because their seeds have a double or even triple skin, quite unconnected with this outer 
cover, but because the latter is analogous to other capsules. 
The loose husky covering of the seed in Carex is surely an arillus; see Engl. Bot. also the 
Rev. Mr. vYood s observations on this genus in Hr. Rees s Cyclopccdia, and Gaertner, v. 1, 13. This 
seed has besides a double testa, though most of the true Grasses have but one, which in ground 
corn constitutes the bran, the husks of the blossom being the chaff.—From Dr. Smith’s admirable 
Introduction to Physiological and Systematical Botany, p. 299. 
