218 T. Holm — Studies in the Cyperacece. 



other species only observable inside endodermis, where it 

 forms a few strata around the mestome-bundles. The arrange- 

 ment of the mestome-bundles is somewhat variable in these 

 species ; in C. dioeca and C. gynocrates, for instance, they form 

 one very regular band, while two in C. exilis,' three in C. 

 Davalliana, and in C. parallela they seem scattered without 

 order inside the endodermis ; they occur mostly as collateral 

 and bicollateral, perihadromatic, together, but in C gynocrates 

 we noticed only the collateral type in specimens from Green- 

 land, Alaska and Canada, while in some rhizomes from 

 Wyoming the mestome-b undies showed a tendency to become 

 perihadromatic. Most of the mestome-bundles in C. Davalliana 

 were observed to be bicollateral, while only a very few showed 

 this structure in C exilis. The pith occupies a very small 

 portion of the central-cylinder in C. parallela and C. Daval- 

 liana and is solid in these species ; in the others, on the con- 

 trary, the pith is larger and broken in the middle so as to form 

 a wide central cavity. 



The stem. 



A triangular and solid stem is generally attributed to the 

 Cyperacece in contrast to a cylindric and hollow culm in the 

 Graminece. There are, however, many exceptions to this rule, 

 and in both orders; we have, already, called attention to the 

 outline of this organ in the " formse hebetatse " of Astro- 

 stachyce being mostly cylindric and hollow inside. Carex exilis 

 is the only species of these in which the stem is triangular, 

 though merely obtusely ; but if we examine the higher devel- 

 oped types we find the stem to be triangular in all the species 

 with the exception of C echinata, in which it is almost regu- 

 larly hexagonal ; the pith seems invariably broken down in 

 these species, as we, also, observed in the lesser devel- 

 oped types. The epidermis is quite thickwalled in all the 

 species and nearly glabrous, the development of prickle-like 

 projections being very scant except in C. elongata. The cor- 

 tical parenchyma consists of short palisades radiating towards 

 the center of the stem in the " hebetatse," also in C. echinata, 

 C sterilis and G. elongata, while in G. Iceviculmis and G. 

 remota the bark is composed of polyedric cells and no distinct 

 palisades ; intercellular spaces are very distinct in all the 

 species, and lacunes are present, one between each two mestome- 

 bundles ; thus the cortical parenchyma does not represent any 

 very firm or solid tissue in these species, and is especially open 

 in G elongata. Stereome occurs as hypodermal on the lep- 

 tome-side of the larger mestome-bundles, besides that it is, 

 also, developed on the hadrome-side of these, where it borders 

 on the pith ; at the smaller mestome-bundles there is less stere- 



