ANATOMY OF ENHALUS ACOROIDES, 961 
developed air-chambers ean be traced from the earliest stage, when the leaf consists 
of one flat layer of mesophyll-cells surrounded by an epidermal layer (Pl. 36. fig. 6). 
This stage is important, as the air-chambers formed are equal in number to these 
cells. Each cell of this layer divides by walls parallel to the epidermis four times, 
so that from each origina] mesophyll-cell a column of five is produced (P1. 36. fig. 7, col). 
The four adaxial cells in each column cut off a small cell towards one side. and then 
later a similar one towards the other side, by walls at right angles to the epidermis and 
parallel to the length of the leaf, so that two columns of narrow cells are formed 
between the columns of wide cells (Pl. 36. fig. 8, d). The small cells then divide by 
walls in the direction of the length of the leaf, producing plates of small cells which 
are the diaphragms of the older leaves (PI. 36. fig. 9, d). The remaining wide cells then 
each divide in half by a wall at right angles to the epidermis, but parallel with the 
breadth of the leaf, forming two cells from each. These increase in size, thus separating 
Fig. 4. 
O 
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BONES 
220; 
the diaphragms and forming air-spaces. Further divisions of a similar nature ron yo 
place, enlarging the air-spaces longitudinally until they appear as long narrow lacu 
(Pl. 36. fig. 10, Z) spanned at regular intervals by diaphragms (fig. 10, d). 5 bae ad viti 
It is interesting, as was discovered by Professor Groom, to note that each spac ie 
the diaphragm-cells at one end and the trabecula-cells between that ELVIS are if 
next is equivalent to one of the original primary mesophyll-celis. So the num 
air-chambers in the mature leaf is determined from the beginning. E ori dhe ba didus 
The abaxial cells of the original columns, except whena bundle is » e Ai Ed re 
into one-half or one-third by walls at right angles to the epidermis and para 
length of the leaf, forming a continuous subepidermal parenchyma. 
