The Cell as a Member of a Group. 39 
If the cells which constitute a tissue are pointed at their 
ends, much longer than broad, and dovetailing into one 
another, the tissue is called prosenchyma. If the cells, on the 
other: hand, are arranged in 
rows, are bounded by flat or 
curved walls, and not much 
longer than broad, it is 
called parenchyma. The two 
_ kinds of tissue frequently pass 
over into one another, and 
may be more or less regular 
according to the mode in 
which the cells have been 
developed (Figs. 60--63). To 
special forms the terms co//en- 
chyma and ‘ tela contexta’ have 
been applied. The former 
usually consists of cells which 
have become more strongly * 
thickened at the corners 
than at the sides ; the thicken- 
-ing-masses are also capable ~ 
of swelling, so that when they 
le in water they appear glossy 
and swollen, and assume a Fic. 62.—Moderately thickened pitted 
gelatinous or mucilaginous hoe ae, the pith of the beech. 
appearance (Fig. 64). ‘Tela 
contexta’ is a tissue in which the simple or branched elon- 
gated thread-like cells are not regularly united to one 
another, as is the case in the kinds of tissues previously 
_ described. ‘The separate cells are in this case arranged 
in threads which do not run parallel to one another, but 
cross irregularly, forming a tissue the separate cells of 
which are not unfrequently grown or cemented together 
_ in anintimate manner and in a variety of ways. This occurs © 
~ in Fungi, Lichens, and some Alge (Fig. 65, p. 42). Some- 
