l8 9 1 -] Anatomical Characters of Uniola. 169 



carene, but merely forms a centre for the entire system of the 

 mestome. It is the strongest one, containing the farthest de- 

 veloped leptome and hadrome, and is supported by the largest 

 group of stereome, but does not, however, connect the superior 

 face of the blade with the inferior. The carene itself consists 

 of two groups of mestome-bundles, one on each side of the 

 median line, and these are all separated from the superior 

 epidermis by an immense tissue of uncolored parenchyma. 

 The uncolored parenchyma preponderates then in this part of 

 the blade and is partly separated from the superior epidermis 

 by six relatively strong bundles of stereome. In the lateral 

 parts of the blade it is restricted to a single stratum inside the 

 rows of bulliform cells. 



As to the mestome bundles, there are in this species about 

 seventy on each side of the median nerve, and they represent 

 three different degrees of development. The largest (fig. 6) 

 are characterized by having a layer of very thick-walled pa- 

 renchyma between the leptome and the hadrome, completely 

 enclosing the first, and both the leptome and hadrome are 

 here strongly developed; furthermore by being supported by 

 two large groups of stereome, above and below, just except- 

 ing the bundles of the carene, where no stereome is in con- 

 nection with the superior face of the mestome. The second 

 degree of development (fig. 8) shows smaller bundles of stere- 

 ome above and below, and the leptome is not separated from 

 the hadrome by any layer of thick-walled parenchyma; there 

 is merely a semicircular layer of thick-walled parenchyma 

 bordering on the leptome side. Fig. 9 illustrates one of the 

 smallest mestome bundles, completely imbedded in the meso- 

 phyll and without any groups of stereome; there is no thick- 

 walled parenchyma to be observed here within the proper 

 parenchyma sheath. 



As regards now the arrangement of these three different 



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forms of mestome bundles, this is as follows: The two larger 

 are constantly situated on each side of the groups of bulliform 

 cells, while the smallest, those of third degree, are restricted 

 to a position just between the bulliform cells and the inferior 

 face of the blade. It must be remarked, however, that this 

 arrangement does not include the bundles of the carene, for 

 the reasons mentioned above. As to the number of these 

 three forms, the smallest ones are the most numerous in the 

 whole blade. It may be expressed diagramatically as follows: 



