84 BRUCE—STRUCTURE AND FUNCTION 
stalked glands or tentacles, which vary in length from small 
ones which require the aid of a lens to be distinctly seen, to 
large ones about 3°5 mm. in length. For a short distance 
behind the leaf-apex, the tentacles do not show any very 
definite arrangement, but occur at irregular intervals all round 
the leaf (Fig. 2). Behind this, however, the tentacles are 
restricted to two definite areas—the under side of the leaf 
along the mid-rib, and the margin of the leaf. : 
The tentacles arise in greatest number either on or near the 
margin of the leaf. Tentacles showing all the variations in size 
mentioned above occur over this area, but the taller ones form 
four well-marked rows—two along each margin, one row along 
its upper, and the other along its lower edge (Fig. 3). 
There is an alternation in size between the tentacles in each 
of these rows ; between each pair of taller ones there is an inter- 
calated one (or it may be two) of about one-third less length, 
and between these in turn is a variable number (six to eight) of 
still smaller ones. These smaller tentacles occur also on the 
margin of the leaf between the rows of longer ones, but they 
never appear on the upper or lower surfaces of the leaf; they 
are much more numerous than the taller ones, and are fairly 
evenly distributed over the specified area in the lower two-thirds 
of the leaf, but above this they diminish in number, while the 
taller tentacles are more numerous and closer to one another, 
until for a short distance behind the apex tall tentacles only are 
present. 
No definite relationship exists between the relative positions 
- of the longer and shorter tentacles of the two rows on the same 
leaf-margin; a long tentacle of one row being sometimes 
situated opposite a long tentacle of the opposite row, but quite 
as often there is no correspondence in position of the long 
tentacles, or there may be one or two small ones opposite a long 
one. There is also no correspondence between the position of 
the long and short tentacles on one margin in relation to those 
on the opposite margin of the leaf. 
A fifth row of tentacles is found on the mid-rib of the under 
side of the leaf (Fig. 3). The tentacles here show variations 
and alternations in size similar to those of the marginal rows, but 
the tallest tentacles are only half (a few may be almost two- 
