ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
741 
Multiple Buds.*' — M. W. Bussell points out that multiple buds are 
in connection through their vascular bundles ; that is, the central 
cylinder of one branches from that which precedes it, as the central 
cylinder of a branch does from that of another branch ; they therefore 
ought to be considered as normal ramifications. 
Structure of the Leaves of Aquatic Plants.| — M. C. Sauvageau 
describes the minute structure of the leaves in the three genera Zostera, 
Cymodocea , and Posidonia. 
If a transverse section of the leaves of Z. marina be made at the 
base of an adult lamina, the epiderm will be found to consist of a con- 
tinuous layer of small cells, the inner walls being thin, and the outer 
wall covered with a thin layer of cuticle, and they contain chlorophyll. 
The epiderm is never in direct contact with the lacunae of the paren- 
chyme, being separated from it by one or two layers of cells. The 
fibrovascular bundles become closer in proportion as they are distant 
from the median bundle, and are each supported by a layer of large 
cells which separate them from the neighbouring lacunae. Between the 
xylem and the epiderm are three or four rows of cells. The marginal 
bundle on each side is near the edge, and is surrounded by a less dense 
tissue. The parenchyme between the bundles contains large lacunae 
running the length of the lamina, and parallel to the veins, sometimes 
bifurcating or fusing, but without changing their disposition or their 
form, as seen in transverse section. 
The leaf of Z. marina is characterized : — (1) by its completely 
closed sheath ; (2) by the 5-9 parallel veins ; (3) by the prolongation 
of the median vein to the apex; (4) by the absence of endoderm or of 
pericycle in the fibrovascular bundles; (5) by the lacunae being dis- 
posed in a single row; (6) by the non-lignified sclerenchymatous 
fibres, which are subepidermal or surround the fibrovascular bundles ; 
(7) by the absence of secretory cells. In Z. nana the general structure 
is very much the same as in Z. marina , but there are only three fibro- 
vascular bundles — one median and two marginal, of which the structure 
is also the same. Between the bundles on each side are 3-6 lacunae. 
The sheath, instead of being closed as in Z. marina , is open throughout 
its whole length, while the ligule is identical. Z. Mulleri replaces 
Z. nana in Australia ; and, as in that species, there are three fibro- 
vascular bundles. 
The genus Cymodocea has been divided into three subgenera, Phycagros- 
tis , Amvhibolis, and Phycoschoenus. In C. sequorea, a Mediterranean plant, 
the leaves are alternate, distichous, liguled, and with long sheaths. There 
are nine veins connected together by anastomosing transverse branches, 
and this species is characterized by the presence at the extremities of 
secretory cells. The epiderm is alike on the two faces, and is composed 
of small cells with fairly thick walls. The leaf of C. sequorea is 
characterized (1) by its sheath with free edges ; (2) by the lamina being 
indented at the edge near the summit ; (3) by the 7-9 veins ; (4) by 
the median vein not quite reaching the apex ; (5) by the presence 
* Comptes Rendus, cx. (1890) pp. 1277-9. 
f Journ. de Bot. (Morot), iv. (1890) pp. 43-50, 68-76, 117-26, 129-35, 173-8, 
181-92, 221-9, 237-45 (38 figs.). Cf. this Journal, 1889, p. 659. 
