82 Gibson. — Contributions towards a Knowledge of 
Following upon the glossopodium comes a thicker swollen 
region whose cells are large, polygonal, and filled with dense 
granular protoplasm, with well-marked nuclei (Fig. 8). The 
long axis of the glossopodium is not in the same plane with 
that of the long axis of the body of the ligule, but cuts it at 
a more or less pronounced oblique angle, the glossopodium 
pointing away from the stem into the base of the leaf, while 
the free portion of the ligule lies almost parallel with the leaf- 
blade. The distal half of the ligule consists of smaller and 
less granular cells, and thins off to the free margin, which is 
unilamellar in the adult condition, the cells there being more 
or less filled with a granular slime. I purpose referring to 
these cells later on. 
Between the glossopodial sheath and the leaf-trace-bundle 
there lie one to several layers of large cells, which radiate 
from the glossopodium outwards towards the leaf and inwards 
towards the stem. In most cases these cells retain their 
cellular character, or at most become slightly thickened and 
pitted ; but in many they become markedly thickened, and 
in the mature condition are transformed into short, often 
branched tracheidqs. In apus, S. stenaphylla , vS. Martensii , 
and others, only a few such secondary tracheides with scalari- 
form markings are formed, so that the leaf-trace appears only 
slightly enlarged just beneath the glossopodium ; but in 
S. Helvetica these tracheidal elements are so numerous that 
the whole glossopodium is enclosed in a distinct cup-like 
vascular enlargement. An intermediate condition may be 
seen in such a form as S. Wildenowii, whilst S. laevigata , var. 
Lyallii , shows the greatest development of tracheides of any 
of the species I have examined. In that species (Fig. 21) 
a very distinct vascular cup is formed, which shows up very 
clearly if the ligule be carefully pulled out of its socket after 
boiling the portion of the shoot selected in dilute potash. 
This curious expansion of the leaf-trace, if it may be so 
termed, has already been noted by McNab ( l. c.), and he doubt- 
less based his theory of the absorptive function of the ligule on 
this fact. I think, however, that the phenomenon in question 
