142 
Anatomy. Stem: Central cylindre of a compound 
bundle with four phloem-parts and common xylem dissolv- 
ing into a central air-cavity. The whole surrounded with 
an endodermis of thinwalled 0-cells. Outside of this we 
have the bark-part with a circle of rather narrow lacunæ. 
On each side, between those lacunæ and the epidermis, 
there is a single vascular bundle. Those two bundles are 
characteristic to our species. The epidermis consists of 
stretched cells, the length about 4— S times the broadness. 
A cross-section of the leaf shows a central vascular 
bundle surrounded by an o-endodermis like that of the 
stem, and on each side of it an air-lacuna. For the rest 
there is a pretty large-celled parenchymatic tissue which 
straight over and below the lacunæ (see the fig.!) consists 
of 3—4 cell-layers. In the very margin now and then some 
few cells are transformed in mechanical purpose, growing 
a little narrower and more thick-walled, but proper bast- 
bundles or vascular bundles we have not been able to dis- 
cover in this species. Consequently the leaves are uni- 
nerved. 
So is also, after our opinion, the case always in the 
R. maritima. R. spiralis , on the other hand, varies as above 
said. Cfr. C. Sau vage au ( 13 ) and C. Raunkiær. 1 . c. The 
differences between here concerned three species lie chiefly in 
the thickness of leaves, which, again, is depending on the thick- 
ness of the parenchymatic tissue surrounding the lacunæ. R. 
maritima presents larger lacunæ separated from the epider- 
mis of the upper and lower surface by a single layer of cells. 
Width and thickness in the relation of 4: 1 or 3: 1. R. spiralis 
(the Baltic var.) with narrower lacunæ, deeper epidermis- 
cells and a two-celled stratum (see the fig.!) occupies an in- 
termediate position. R. obtusa has also narrow lacunæ but 
still thicker, 3— 5-celled walls, and the above said relation 
between width and thickness can be expressed by 2: 1. Thus 
the three species present a different leaf-anatomy, whereas 
R. br achy pus » in the stem- and leaf-anatomy corresponds 
