222 MISS Е. S. BARTON ON THE GENUS TURBINARIA. 
II. Leaf.—The leaf of Turbinaria, reduced to its simplest form, as found in 
T. Murrayana and іп T. tricostata, which have no vesicle, appears to be a triangular 
shield or disk supported by a petiole, which joins it at the centre—a peltate leaf, in short. 
In the other species, of which 7. conoides may be taken as the type, the matter is 
complicated by the development of a vesicle at the junction of stalk and lamina. When, 
in addition to this, the petiole is furnished with wings, as in T. trialata, and the vesicle is 
inflated, the appearance of a peltate leaf is much disguised. Іп T. dentata, which has 
distended vesicles and only a row of teeth, in place of regular wings, this character is 
harder to trace. The species of Turbinaria, however, fortunately for this purpose, run 
into each other in these points, and it is as easy to trace through the different species 
such gradations of form as it is difficult to draw hard-and-fast specific distinctions founded 
on these modifications. 
The petiole consists of the same three layers of tissue (Pl. LIV. fig. 9) as the stem, and 
each tissue is continuous, the one with the other. Both in the central strand, however, 
and in the cortical parenchyma the cell-walls are much thinner than the corresponding 
tissues of the stem. The epidermal layer is continuous throughout. 
Тһе central tissue divides near the base of the vesicle into three distinct strands, and 
these run up the inside of the vesicle like the ribs of an inverted umbrella, subdividing 
meantime into numerous lesser strands, which anastomose and form a framework for 
the vesicular tissue. Ав they reach the lamina the subdivisions increase in number and | 
run out to the edge, where they disappear and are lost in the parenchyma of which the 
lamina is composed (Pl. LIV. fig. 10). That part of the lamina which forms the roof of 
= vesicle is composed entirely of epidermis and parenchyma, and contains no fascicular 
issue, 
In comparing the leaf of T. conoides with a specimen of T. ornata devoid of vesicles, I 
found the course of the bundle slightly different in T. ornata, as might be expected. 
About halfway up the petiole the conducting tissue spreads out into the form of a 
triangle, the centre being filled with a large-celled medullary parenchyma, resembling 
the cortical tissue. From this triangle, the corners of which are marked by a large 
group of these small cells, strands run up the underside of the lamina (there being no 
vesicle in this species), and, as in 7. conoides, gradually disappear as they approach the 
margin of the leaf. The three corners of the triangle are protected on the Jower side by 
one Mem support the lamina and give it a triangular shape. (Compare РІ. LIV. 
eo з. — are formed by a rending apart of the 
cells run parallel to-one ы а the т. itid sie i : > RERE 
NL d p the petiole anto the lamina, which is then no broader 
ws и of „оо п esae ek ее А stari арн 
чай секта арайы тар i rtis e found in the half-formed cavity. In older 
ping ако) Ps Зоот m ирнен the cells bordering the edge of the 
‘fig. 1); lastly, in the full са : йы > e 2. 2 miim 
ам idis ле ы. ^us vesic ев а cuticle peels off the internal surface of the 
, eath this cuticle grow out and protrude into the empty 
