72 SIR DIETRICH BRANDIS ON THE 
in full-grown leaves of any one species. In some species, however, they are much 
narrower than in others; instances are Phyllostachys mitis, Rivière, and Dendrocalamus 
strictus, Nees. And I have found a remarkable case of abnormal structure in specimens 
of Melocanna bambusoides: the leaf is dwarfed, the space between longitudinal nerves 
much reduced, and the apparent cavities small, the two sometimes confluent into one. 
BULLIFORM CELLS. 
It will be convenient to commence the study of the bulliform cells at an early stage 
of their development. Pl. 12. fig. 17 represents the youngest leaf of Dendrocalamus 
giganteus, Munro, rolled up in bud. What may perhaps first of all attract the attention 
of the reader is a matter of no importance, which we had better dispose of at once. The 
lower (in the rolled-up leaf, outer) epidermis is uneven with protuberances and hairs. 
This is a general character of all Bamboos. But in the present case there are also hairs 
on the upper epidermis. These, however, are only there in the youngest state; after- 
wards, as the leaf matures, they dry up and fall away. The upper epidermis of mature 
leaves in Bamboos, with a few exceptions, is quite smooth. The vascular bundles 
(longitudinal nerves) are fully developed, so are the apparent cavities and the cells of the 
chlorophyll-containing tissue, as well as the upper and lower epidermis: the bulliform 
cells, however, are scarcely beginning to be differentiated from the other cells of the 
upper epidermis; they are indicated by a longitudinal furrow. A section of a leaf 
a little older is represented on Pl. 12. fig. 16. Here the bulliform cells begin to show, 
but they are still situated in a longitudinal furrow. At a later stage, when the leaf is 
flattened out, they increase in size and are raised above the surface of the epidermis, 
figs. 12, 13, 14. A similar development in the case of Melocanna bambusoides is repre- 
sented in Pl. 13. figs. 29, 30, and Pl. 14. fig. 31. 
The leaves of all Bamboos, so far as known to me, have vernatio convoluta, that is, 
the leaf is rolled up in bud and afterwards spreads out flat. ^ Chusquea pinifolia, Nees 
(Pl. 14. fig. 39), may possibly be an exception. As clearly explained by Duval-Jouve 
(* Histotaxie des feuilles de Graminées, p. 322), the spreading out flat of grass leaves 
with convolute vernation is greatly facilitated by the development of the bulliform cells. 
'Tschirch (1882) ascribes to the same cells certain other functions in connection with the 
rolling up of the leaves of some species, when the plant is dry (‘ Jahrbücher für wissen- 
schaftliehe Botanik, xii. p. 514), and he gives them the name of Gelenkzellen or 
Gelenkpolster (link-cells). In this he is followed by Güntz (1886), p. 16, and by 
Raunkiær (1895-1899), who calls them Ledcellerne. Volkens (1887), Fl. Aegypt.-Arab.. 
Wüste, p. 55, describes the leaves of Cynodon Dactylon and other species, which have, in 
continuation of the bulliform cells of the upper epidermis, a tissue of thin-walled colour- 
less cells separating the rings of chlorophyll parenchyma that surrouud the longitudinal 
nerves. When leaves of this description are dry they shrivel up, because the transverse 
bands of colourless cells collapse. When supplied with water they resume their former 
turgescence. Accordingly Volkens regards these bands of colourless thin-walled tissue, 
consisting partly of bulliform cells, as water-cells (Wasserzellen). 
