4 J 



3G2 HoL.M : Juncus repens Michx. 



■ 



the mestome-shcath of the ribs are small stcrcome-groups to be 

 observed of relativcl}- thin-walled cells, separated from epidermis 

 by mesophyll. In Fimbristylis on the other hand the stereome is 

 sub-epidermal and is not in contact with the ribs, these beint^ 



"pure mcstomc-bundles." The mestomc-bundles (Plate 363, 

 Fig. 3) are surrounded by a colorless, thin-walled parenchyma- 

 sheath, which, on the leptome- and hadrome-side, is Interrupted by 

 stereome. Inside of this sheath follows a mestome-shcath of dis- 

 tinctly porose and thick-walled cells, which is perfectly closed and 

 directly surrounds the leptome and hadrome. If we examine the 

 smallest bundles in the same leaf we notice a similar structure, but 

 the mestome-sheath is less conspicuous since only a few of its 

 cells are thick-walled. The drawing (Plate ^C^i, Fig. 4) shows only 

 one slightly thick-walled cell on the hadromc-side and three on 

 the leptome, the other part of the mestome-sheath being thin- 

 walled similar to the parenchyma-sheath outside. 



In comparing this structure of the mestomc-bundles in our 

 JiDiais with those of Fimbristylis, we notice the total absence of 

 the inner chloroph}-ll-bearing sheath m Jiaiciis. This sheath which 

 we have described and figured in a paper on FiiiihyistyUs {Aiucr. 

 Jortr. of Science, 1899) seems characteristic of a number of C}'per- 

 aceae, but its dev^elopmcnt does not appear to depend on any 

 certain shape or position of the leaf-blade. In Juncus rcpcns the 

 linear leaf-blade, as described above, is held in exactly the same 

 position as that o{ Fiinbristylis autunuialis, bedsides that these plants 

 inhabit much the same localities, yet the leaf-structure is differ- 

 ent in both. It is evident that the inner chlorophyll-bearing 

 sheath is characteristic only of certain Cyperaceae, and perhaps 

 only of those in the leaves of which the mesophyll is restricted to 

 palisade sheaths around each individual mestome-bundle. 



The leaf o{ Juncus rcpcns, in the terrestrial form, is as we have 

 seen from the above bifacial and shows a rather open structure on 

 account of the wide lacunes. If we examine the submerged form we 

 observe the same structure and a similar position occupied by the 

 leaf-blade, but the lacunes are much wider and tlic cells of epider- 

 mis of the upper face are not much larger than those of the lower. 



In regard to the internal structure of the prostrate stem (Plate 

 3^^3j F^i^- 5)» this corresponds in most particulars with that of the 

 erect, flower-bearing one. The prostrate stem, however, is broader 



