l l° The Botanical Gazette. [June, 



A*-C-B-C-A-C-B-C-A 1 -C 1 -B 1 -C 2 -B 2 -C 3 -A 2 , 

 where A indicates the largest bundles of mestome, the me- 

 dian being A*; B shows those of second and C those of third 

 degree. A : corresponds then to the strong bundle in fig. 2, 

 marked in the same manner, and it is situated below the out- 

 ermost group of stereome in the figure, separated from this 

 by the uncolored parenchyma. C 1 is the first bundle situated 

 between the first group of bulliform cells and the inferior ep- 

 idermis. The disposition of the groups of bulliform cells may 

 be seen in the same formula, namely, between A 1 and B 1 , 

 B 1 and B 2 , B 2 and A 2 , just above the C's, beginning at C 1 . 

 This formula may not be strictly constant, but it gives, how- 

 ever, the general features concerning the relative number and 

 arrangement of the mestome bundles. 



Besides the proper parenchyma sheath of green or some- 

 times uncolored cells, never wanting in the mestome-bundles 

 of the Gramineai, some of these bundles show the presence 

 of another sheath or at least a layer of thick-walled parenchyma 

 inside this. A distinct thick-walled sheath is shown in fig. 6. 

 enclosing the leptome, and we are able to trace it also in the 

 small bundles (fig. 8), though not in the smallest ones (fig- 9)- 

 Schwendener 10 has called attention to the presence of this 

 parenchyma, which in several instances looks very much like 

 what the same author has called a - mestome- sheath." But 

 in Umola latifoha there is no mestome-sheath; for the reaction 

 with concentrated sulphuric acid proved that the thick-walled 

 cells, whether they form a closed sheath or not, merely be- 

 long to the mestome parenchyma. Furthermore, if it had 

 been a mestome-sheath it would also have been present in the 

 smallest bundles The proper parenchyma sheath showed in 

 some instances (fig. 7), a thickening of the cell-walls, especi- 

 ally in the cells which border on the leptome side. 



Now, concerning the arrangement of the stereome-bundles, 

 we have already seen in the description of the mestome that 

 the arrangement ,s nearly identical. There is one group 

 above and below the two largest mestome-bundles, but none 

 at the smallest ones, and there are merely six isolated groups 

 on the superior face of the carene, which are not in contact 

 with the mestome Besides there is also one rather strong 

 group in each of the outermost parts of the blade, the 

 margins. 



10 S. Schwendener; Die MestomscheidprwwT-Z : 7~, 7T- T 



berichted. wiss. Acad. Berlin. lS) Gr amineenblaetter. (Sitzungs 



