CHAP. T. 
OF THE ELEMENTARY ORGANS. 
7 
be sometimes capable of extension with the same rapidity as 
the membrane among which it lies, and to which it usually 
adheres ; but it occasionally elongates less rapidly, when it is 
broken into minute portions, and is carried along by the 
growing membrane. In direction it is variable (Plates I. 
and II.) ; sometimes it is straight, and attains a considerable 
length, as in some fungi; sometimes it is short and straight, 
but hooked at the apex, as in the lining of the anther of Cam- 
panula ; occasionally it is straight, and adheres to the side of 
membrane, as in the same part in Digitalis purpurea ; but its. 
most common direction is spiral. Whether it is solid or hol- 
low is not quite settled ; Purkinje asserts that it is hollow, as 
will be hereafter mentioned ; but there can be no doubt that 
it is also, at least sometimes, solid, as in the fibrous utricles of the 
leaf of Oncidiumaltissimum ; and I have every reason to believe 
that it is always so, an opinion equally entertained by Valen- 
tin, Schleiden, and Morren. Elementary Fibre has a constant 
tendency to anastomose,- in consequence of which reticulated 
appearances are frequently found in tissue. Slack adds that 
it sometimes branches. Like membrane it is increased in 
thickness by the deposit of sedimentary matter on that part 
which does not adhere to the membrane, as has been proved 
by some beautiful microscopico-chemical experiments of 
Schleiden. 
Of the organic mucus, membrane, and elementary fibre 
thus described, all the elementary organs of plants are con- 
structed. For the convenience of description, they may be 
considered as of five different kinds, 1. Cellular tissue^ or 
Parenchyma', 2. Pitted tissue, or Botlirenchyma ; 3. Woody tissue, 
or Pleurencliyma; 4. Vascular tissue, or Traclienchyma ; b, Lati- 
ciferous tissue, or Cinenchyma* 
* Profe.ssor Morren has proposed the following nomenclature of tissue, 
which has some advantages over that now more commonly in use. I. Pa- 
renchyma ; 1. merenchyma, or sphcBrenchyma, spherical; 2. conenchyma, 
conical, as in hairs ; 3. ovenchyma, oval ; 4. atractenchyma, fusiform ; 
5. cylindrenchyma, cylindrical; 6. colpenchyma, sinuous; 7. cladenchyma, 
branched ; 8. prismenchyma, prismatical. II. Perenchyma, amylaceous 
granules. III. Inenchyma, fibro-cellular tissue. IV. Angienchyma, 
vascular tissue; 1. pleurencliyma, tissne ; 2. trac^encliyma, spiral 
vessels ; 3. modified traclienchyma, ducts ; 4. cinenchyma, laticiferous vessels. 
B 4 
