6 T. Holm— Studies in the Cyperacece. 



The rhizome. 



While the ramification of the stem underground is sympodial 

 in our species, we may, nevertheless, distinguish three forms 

 or modes of growth, viz: cespitose, creeping and tuberous. 

 The first of these is exhibited by 8. verticillata, and partly, 

 also, by 8. reticularis and 8. Torreyana, and does not differ 

 from the usual cespitose rhizomes of other Cyperacese. 8. 

 ciliata md S. hirtella have creeping rhizomes reminding one 

 of Fuirena scirpoidea, which we have described in a previous 

 paper.* The third form, the tuberous, is well exemplified by 

 8. pauciflora and partly, also, by S.filiformis and 8. Elliottii. 

 In these species we notice that the rhizome is very much 

 branched with relatively short internodes, densely covered by 

 rudimentary sheathing leaves. The two basal internodes of 

 each flower-bearing shoot are, furthermore, distinctly swollen 

 so as to give the whole rhizome a peculiar knotted appearance. 

 It is the basal internodes of the axis of first order that show 

 such swelling, while the secondary axis grows out as a short, 

 creeping and rather slender branch. 



The development of these forms of rhizomes does not seem 

 to depend upon the character of the soil, since the creeping is 

 noticed in damp (8. hirtella) as well as in very dry sandy soil 

 (8. ciliatd). The cespitose form is especially characteristic of 

 8. verticillata, which was collected in damp soil, like 8. reticu- 

 laris and S. Torreyana. The third form is common to species 

 from dry, sandy to rich or swampy ground. Examining the 

 internal structure of the rhizome of 8. pauciflora, we notice a 

 thick-walled hypoderm of about three layers inside the epi- 

 dermis, and bordering on a large bark-parenchyma of thin- 

 walled cells, which contain deposits of starch. The endodermis 

 is not very well differentiated, but seems to consist of rather 

 irregular, thick-walled cells. The innermost part of the rhi- 

 zome consists of a large, starch-bearing fundamental tissue in 

 which a number of collateral and perihadromatic mestome- 

 bundles are imbedded, each of which is surrounded by layers 

 of stereome. A corresponding structure is, also, noticeable in 

 the tuberous base of the stems, but in these we observed a dis- 

 tinct and thin-walled endodermis, and noticed that the stereome 

 around the mestome-bundles is only weakly developed. 



In 8. ciliata and 8. hirtella we find a similar structure, but 

 the cells of endodermis are more thin-walled. The stereome 

 when compared with that of 8. paucijlora is much heavier in 

 8. hirtella, and much weaker in 8. ciliata. Reservoirs of tan- 

 nin were observed in all three species, and seemed to be espe- 

 cially abundant in the bark and fundamental tissue of 8. ciliata. 



*This Journal, vol. iv, July, 1897, p. 25. 



