THE LEAF 
31 
Spongy chlorenchyma. ‘The lower portion of the chlorenchyma 
is known as spongy chlorenchyma and is usually composed of cells 
which are more irregular in shape and arrangement than the 

Fia. 20. Section, cut parallel with the epi- 
dermis, through the spongy parenchyma 
of a leaf (Hibiscus). (x 425) 
palisade cells (Vigs. 17, 
20, 28). Also, this region 
generally contains large 
air spaces. The cells of 
the spongy chlorenchyma 
contain chloroplastids and 
carry on photosynthesis, 
but they are not in as 
favorable a position for 
receiving light as are the 
palisade cells, and they 
have fewer chloroplastids. 
They are not, therefore, 
so important from the 
standpoint of photosyn- 
thesis as are the palisade cells. On the other hand, the large 
air spaces that surround these cells are near and directly con- 
nected with the stomata (Fig. 17). There is, therefore, a much 
freer circulation of gases around 
these cells than around the palisade 
cells, with the result that they are 
better suited to the exchange of 
gases between the cells and the sur- 
rounding atmosphere. The air spaces 
of the spongy chlorenchyma are not 
isolated chambers but a series of in- 
tercommunicating passages. While it 
is customary to speak of the air spaces 
in the spongy chlorenchymaas though 

Fia. 21. Rosette crystal from 
cell in a leaf. (x 730) 
there were many of them, it would be just as correct to consider 
many of them as forming a single large air space in which, in the 
case of the spongy chlorenchyma, the cells are loosely arranged. 
A good idea of the shape of these passages can be obtained 
