PARENCHYMATOUS AND PROSENCHYMATOUS CELLS. 39 
cally. Among the forms resulting from an extension of the cell 
in an horizontal direction, we need only mention tabular cells 
( figs. 68 and 94), that is, six-sided flattened cells, with the upper 
and lower surfaces parallel, or nearly so. Of those cells, which 
are extended in length or vertically, we have such forms as the 
cylindrical (fig. 69) and fusiform (fig. 70), and which, by the 
mutual pressure of contiguous cells, often become prismatic. | 
In the Fungi and Lichens again we have a very marked form. 
Thus the cells are here thin-walled and very long and thread- 
like, and either simple or branched (jig. 71). Such cells are 
sometimes termed fibrilliform, (see page 48). 
The cells, when in combination with other cells so as to form 
a tissue, are generally bounded by more or less flattened ( jigs. 
65, 66, 68, and 69) or rounded surfaces (figs. 62 and 72); but 
Fic. 70. 
‘Fia.68. Tabular cells.— Fig. 69. Cylindrical cells. The small rounded body 
in the interior of three of these cellsis the nucleus. Fig. 70. Elongated 
fusiform cells.——fig. 71. Fibrilliform cells (hyphe). 
when in combination also with the vessels of the plant, so as to 
form what are called the fibro-vascular bundles, they are elon- 
gated, and have pointed extremities (fig. 70). These variations 
in the condition of the cells lead to corresponding differences 
in their arrangement ; thus, in the former case, the cells are 
placed one upon another (jig. 69), or side by side (fig. 68) ; 
while in the latter their tapering extremities overlap each 
other, and become interposed between the sides of the cells 
which are placed above and below them (jig. 70). From this 
circumstance cells have been divided into parenchymatous and 
prosenchymatous ; parenchymatous being the term applied to 
those cells which are placed end to end or side by side; and 
prosenchymatous to those which are attenuated, and overlap 
