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38 INTRODUCTION TO BOTANY.
posed of an elastic membrane rolled up like the spring of
a bell into a cylinder, abundant in young shoots ; supposed
to convey air. PL 1. fig. 5. i.
a. 4. Mixed vessels, Fasa mixta. Tubes of a mixed
nature, in some parts dotted, in others streaked or spiral.
b. Vasa adducentia spiralia^ Pasa chymifera, Fasa hydro-
Sera. The spiral thread forming the air vessels; consiered
by Hedwig as a distinct species of vessels itself.
c. Proper vessels, Fasa propria, Receptacula sued proprii.
Cavities dispersed in the cellular texture, closed on all
sides, and filled with some peculiar juice.
c. 1. Bladdery reservoirs, Receptacula vesiculosa^ Glandular
vesiculares. Spherical bladders, usually Contain essential
oils, dispersed in the parenchyma of the leaves, or
bark. .Myrtus communis. Citrus Aurantium.
c. 2. Blind reservoirs, Receptacula cceciformiai Fitter.
Short tubes, filled with essential oils, as in the bark of the
seeds of umbelliferous plants.
c. 3. Milk vessels, Turpentine vessels, Receptacula tu-
hulosa, Fasa propria solitaria. Single tubes in the cellular
texture, filled with a milky, or turpentine juice.
c. 4. Fascicular reservoirs, Receptacula fascicularia, Fasa
propria fascicularia. Bundles of small parallel tubular
cells, filled with a peculiar juice ; as in the bark of apo-
cineae.
c. 5. Accidental reservoirs, Receptacula' accidentalia.
Accidental cavities, into which the juices formed in other
parts has filtrated : in the coniferae the turpentine frequently
bursts its own vessels, and penetrates the pith and sap-
vessels.
Tubular openings. Open spaces of the pith, LacuuO!,
Cavitates aerece, Fasa pneumatica, Receptacula aerea accidentalia.
Cavities filled with air, frequently found in the
cellular texture, formed by rupture or absorption.
1. Irregular, L. irregulares. Found in the middle of the
fleshy parts of plants. PI. 1. fig. 5. k.
'2. Fistular, L.fistuloscB. Occupy the centre of the stalk,
and render it hollow like a flute. Gramineae.
3. Regular, L. regulnres. Occupy the centre of the stem
of water plants, the cells being disposed in a regular order.
Scirpus.
4. Cellular, L. cellulares. Large cavities, of which the
sides are themselves composed of cellular texture. Sparganium.