1896. ] Anatomical Characters of N. Am. Graminee. 359 
tiated parenchyma sheath, while the mestome sheath is very 
well developed, perfectly closed, and thick walled as in all 
the other mestome bundles. There is only one vessel in this 
bundle and a small group of leptome. These small bundles 
were observed only in the keel, in the parenchymatic layers 
which connect the two surfaces of the keel with each other, 
bordering on the large lacunes (Z, fig. I 
In regard to the general distribution of these various forms 
of mestome bundles in the leaf-blade of Oryza, those of the 
third degree are the most numerous, while those of second de- 
gree are less so; these last constitute the very rough ribs, 
which are so prominent on the upper surface of the leaf. 
The stereome has attained a large development in this 
grass, and forms layers above and below all the mestome 
bundles of the lateral parts of the blade; as we have seen in 
figure 1, there is no stereome on the inner side of those mes- 
tome bundles which are situated in the keel. The margins 
which Haberlandt? has designated as ‘‘Armpallisadenzellen 
(fig. 3), in which the cell wall shows deep foldings inwards. 
his orm of tissue has been observed in representatives of 
widely separated families of the vascular plants, e. g. Anemone 
and several other Ranunculaceez, Bambusa, Arundinaria and 
Filices, Equisetum, etc. Haberlandt has explained the 
Physiological signification of this peculiar folding of the cell 
Wall in this way, that thereby the inner surface of the cell be- 
‘omes considerably enlarged so as to be able to give space for 
1 Increased number of chlorophyll-grains. 
The mesophyll in Oryza forms isolated groups between the 
eome bundles, and surrounds the large lacunes of the 
el, 
The colorless parenchyma is very well represented as we 
oe already seen above from the description of the mestome 
| Sundles and their surroundings. We have discussed the col- 
| of tissue above the mestome bundles, and finally the 
2 £ ioe 
G. HABeRLanpt: Physiologisches Pflanzenanatomie 174. Leipzig 1884. 
