486 Mr. VALENTINE on the Structure and Development 
of the sporule, where they lie quite concealed by the germ, little fibrille or 
rootlets begin to shoot from one side. They are simply articulated tubes, or 
elongated cells applied end to end, with frequently a bulbous extremity ; and 
each is produced from one of the cells of the germ (Tas. XXXIV. fig. 14.). 
They differ much in length in different sporules; in some they are not longer 
than the sporule, whilst in others they are three or four times that length, and, 
in common with the cells of the germ, contain granules, which in these are 
colourless, but in the germ green. "The cluster-like appearance of the cells 
which form the germ soon after the appearance of these fibrillæ, begins to 
change, the cells becoming flatter and more intimately connected with each 
other. At the same time an internal change is taking place, for by a gradual 
arching or receding upwards of that part of the germ which closes the cavity 
of the sporule the germ becomes hollow, the hollow communicating with the 
cavity of the sporule, which is of course proportionably enlarged (Tas. XXXIV. 
fig.16.). The germ now gradually points in two places, which are by no means 
fixed, but occur in various situations according to the position of the sporule 
in relation to the light. "The direction of the first leaf is generally in the di- 
rection of the axis of the sporule, or rathera little inclined ; and that of the first 
root at right angles, or lateral, but very soon changing to an opposite direction 
to that of the leaf. This would be the constant direction if the sporules were 
always left to themselves, free from entanglements, on account of the peculiar 
structure of their outer coats, the spongy fibro-cellular texture of the superior 
third of which, causing that end to be the most buoyant in the water, exposes 
the superior surface of the germ to the direct action of the light; but as it 
cannot always happen that the sporules should be free, the direction of the leaf 
and root is sometimes quite the reverse, and at others both leaf and root are 
lateral, but proceeding from opposite sides of the germ. These two points 
gradually lengthen, and, if dissected, each will be found to consist of a closed 
sheath, containing in one instance the leaf, in the other the root, in the form 
of a conical process like a finger in a glove. The young leaf, which is taper, and 
has its cells crowded with green granules, being in advance of the root, which is 
obtuse and destitute of green granules, bursts through the summit of its sheath 
when it has become rather longer than the sporule; whilst the root, although 
more backward in its development, pierces its sheath before it becomes as 
