220 The Botanical Gazette. [August, 



while in U. Palmeri the epidermal expansions are merely 

 represented by wart-shaped, obtuse organs. The epidermis 

 of the inferior face is on the contrary entirely smooth in these 

 two species. 



Stomates are present on both faces, but especially on the 

 margins of the deep sinuses of the superior face, in the 

 strata which border on the bulliform cells ; these stomates 

 show in U. paniculata the normal aspect, but in U. Palmeri 

 they are slightly depressed below the general surface (plate 

 xxil, fig. 14), and surmounted by wart-shaped expansions 

 from the epidermis in groups of as many as seven. The 

 bulliform cells of U. gracilis and U. nitida agree very well 

 with those described for U. latifolia; in U. paniculata and U. 

 Palmeri they form only very small groups, but are here in 

 contact with a large mass of uncolored parenchyma. 



Mestome-bimdles. — The arrangement of these is easily to 

 be seen, if the sections figured in the accompanying plates 

 are examined. Plate XXI, fig. 1 shows a section of the 

 median part of the blade of U. gracilis; plate XXII, fig- 7. a 

 similar section of U. nitida; fig. 8 of U. paniculata; and fig. 

 1 3 of the female plant of U. Palmeri. It must be remarked 

 here that the anatomical structure of the leaf of the male 

 and female plant of U. Palmeri is identical. 



The carene in U. gracilis and U. nitida is occupied with 

 but a single mestome-bundle, whereas there were several in 

 U. latifolia. In U. paniculata and U. Palmeri there is no 

 carene and the median nerve is not different in any respect 

 from the largest ones in the whole blade. Furthermore there 

 are no mestome-bundles between the groups of bulliform 

 cells and the epidermis of the inferior face, as was the case 

 in U. latifolia. 



The minute structure of the mestome-bundles in U- 

 gracilis and U. nitida is the same. There is a thin-walled 

 parenchyma-sheath around the entire bundle, uncolored in 

 the midrib or partly green in the other ribs. Sometimes, as 

 for instance in the large bundles excepting the median one. 

 the parenchyma-sheath has a few thick-walled cells, where it 

 is in contact with the stereome. But besides this, the proper 

 sheath is also to be seen and inside this another one, which 

 consists of very thick-walled cells, forming in the largest 

 bundles, those of first degree, a closed sheath around the 

 leptome and the hadrome. This inner sheath is also present 

 in the smaller bundles, but is here more or less interrupted 



