222 The Botanical Gazette. [August, 



Although not strictly belonging to the mestome-bundles, it 

 may be mentioned here, that there is in the U. paniculata a 

 quite considerable tissue of large-celled parenchyma between 

 the hadrome and the stereome of the superior face, and this 

 parenchyma contains starch, like the surrounding sheath. 



We shall also find in these two species a certain difference 

 as to the development of the mestome-bundles, as described 

 for the preceding species. U. paniculata shows two degrees, 

 the first one as described above; the second is on the contrary 

 characterized by having the leptome and hadrome in contact 

 with each other. U. Palmeri shows, besides the form of the 

 first degree described above, a second one, in which the in- 

 ner sheath is reduced to a horse-shoe shaped layer on the lep- 

 tome side, besides a few thick-walled cells between the lep- 

 tome and hadrome but none in the leptome itself. 



These layers of thick-walled cells in the mestome-bundles 

 of U. paniculata and U. Palmeri, whether they form a closed 

 sheath or not, are identical with those mentioned for the pre- 

 ceding three species, as representing a mestome-parenchyma; 

 the same is the case with the groups of similar cells, which we 

 have seen in the leptome of U. Palmeri. Concerning the dis- 

 tribution of these different mestome-bundles in the U. pani- 

 culata and U. Palmeri, those of the second degree are the 

 most numerous, but no rule can be given as to their situation 

 between the larger ones. 



The stereome. — This forms in U. gracilis and U. nitida two 

 groups, one above and one below each mestome-bundle, and 

 shows only very small differences. In U. gracilis the stere- 

 ome of the superior face of the carene is widely separated 

 from the mestome-bundle by a large tissue of uncolored par- 

 enchyma, while in U. nitida it borders immediately on the 

 parenchyma-sheath. It forms as in U. latifolia a nearly tri- 

 angular group on each margin of the blade. Nearly the same 

 arrangement is found in U. paniculata, in which there is one 

 group above and below each mestome-bundle. In this the 

 stereome of the superior face is widely separated from the 

 mestome-bundle by the parenchyma, which has been described 

 above. Small groups of stereome are also to be observed in- 

 side the proper parenchyma-sheath of this species (plate XXII, 

 fig. 9); it seems as if these thick-walled cells belong to this 

 element, the stereome, rather than to the hadrome. 



Finally U. paniculata shows groups of stereome opposite 

 the bulliform cells, separated from these by an uncolored ti>- 



