36 Arber .— On the * Squamulae Intravaginales' of the Helobieae . 
Potamogetonaceae — Cymodocea . 
I have not made any thorough study of this genus, but I include it here 
because, in serial sections through an inflorescence of Cymodocea isoetifolia , 
Asch., I noticed the development of squamulae intravaginales in connexion 
with the prophyll of a lateral branch ; their origin is illustrated in Figs. 
4 A-E. Figs. 4 A and B show the main axis, with a bulge on the side on which 
a lateral bud (b.) is about to*develop; the margins of its prophyll (sh. and 
ski) are beginning to detach themselves. In Fig. 4 c we reach the level at 
which the lateral bud is completely free, but the prophyll (pr.) is still attached 
to the bud on the adaxial side. Squamules ( sq .) are seen developing from 
the angle between the prophyll and the axis of the bud. When they are 
Fig. 4. Cymodocea isoetifolia , Asch. Figs. 4 A, B, C, E, series of transverse sections (x 23) 
passing upwards from below through an axillary hud, b. (whose further history has not been followed), 
and its prophyll, pr ., borne laterally on an axis, ax. Figs. 4 A and B show detachment of margins 
of prophyll, sh. and sh.' Fig. 4 c, complete detachment of lateral bud, from which the prophyll is 
at this level only partly free; dotted line indicates plane of separation between prophyll and axis of 
bud ; sq ., squamule. Fig. 4 d, region to left of arrow in Fig. 4 C ( x 77 ). Fig. 4 e, stage at which 
bud, squamules, prophyll, and parent axis have become free from one another. || 
examined in detail, it is found that they arise from the tissues of the bud- 
axis, and not from those of the prophyll; this point is illustrated in Fig. 4D, 
which represents the part of Fig. 4 C to the left of the arrow, on a larger 
scale. 
Scheuchzeriaceae— Triglochin. 
Figs. 5 A, c, F, G, H, from serial sections of a bud of Triglochin mari- 
tima , L., show, at different levels, the relations of the young leaves and the 
associated squamules. Fig. 5 A is a slightly oblique transverse section in 
which the sheath of the outermost leaf (/. T ) has detached itself on the left- 
hand side, but is still one with the axis on the right. Only a few of the 
squamules external to it are included in the section. The further history of 
the leaf, up to the point of separation of the ligular sheath {tig. j #1 ) and the 
petiolar limb (pet.P) can be followed in Figs. 5 c, F, G, H. But from 
our present point of view it will be simplest to concentrate attention on 
the second leaf and the squamules immediately outside it. In Fig. 5 c' 
this leaf (/. 2 ) is free on the left-hand side, but still fused with the young 
axis on the right. The leaf is surrounded by squamules, of which those 
