MISCELLANEOUS. 
101 
each other. These sacs are hexagonal, round, or oblong, 
flattened or spiral formed (Cucurhita pepo.), ramified (Ficus 
elastica), &c., &c. They either have simple walls, or are 
covered, internally, with free spiral formed tmsted fibres 
(lames), or the fibres are combined (sendees), and form slits 
(utr. scalariformes), or they form large and narrow holes, 
which are regularly or irregularly distributed (utr. poreuses). 
Further, they are, when developed, empty, as in the pith (areo- 
laires), or full of juice (succulentes), or they contain a coloured 
juice, which thickens, and renders the walls thicker (utr. paren- 
chymateuses). The vessels are of a twofold kind ; — 1st, Proper 
vessels or bark-vessels, which carry a more or less coloured 
juice : 2d, Trachene, central, or wood- vessels. The tracheae 
have a fibre in the interior, which lies close to their walls ; 
this fibre is free, twisted in a spiral form, and may be un- 
rolled in the true tracheae, or it is double, either with edges 
that are remote from, or touch each other ; or the edges are 
here and there entwined with the false tracheae, or with the 
cranny like vessels (v. fendus) ; or they are intergrown with 
each other, in a manifold manner, as in the porous vessels. 
The tracheae sometimes consist of small pieces, which are 
joined to each other at their ends (v. articules). These dif- 
ferent forms are frequently found together in one and the 
same vessel, but one form never changes itself into another. 
Dicotyledons . — The stems of Dicotyledons, at the commence- 
ment of their formation, are formed of a transparent, juicy, 
imperfectly developed organized cellular tissue. They soon 
exhibit more juicy and coloured points, which in definite num- 
bers constitute the parenchymatous bundles. These bundles 
contain vessels of a twofold kind ; — 1st, Proper vessels, which 
are placed towards the circumference, and especially towards 
the external circumference : 2d, Trachese, which are situated 
in the interior of the bundles. The parenchymatous bundles 
are situated in the pith of the stem, and are divided into 
three parts, the central pith, the medullary rays, and the 
bark. The first period of growth follows. A transparent 
intervening space exhibits itself between the two vascular 
groups of the parenchymatous bundles, which is only an 
493 
