

iSo BOTANICAL GAZETTE [September 



by reason of fusion of leaf traces with other strands may continue in 

 their amphivasal condition from one node to another in case the inter- 

 nodes are short j as is the case in a stocky stem such as occurs in this 

 genus. The leaf traces are collateral and penetrate the cortex rather 

 rapidly to enter the central cylinder. Fig. 2J shows a transverse sec- 

 tion through the floral axis. The exceedingly dicotyledonous looking 

 ring of collateral bundles cannot fail to be remarked. Attention has 

 already been called to the persistence of ancestral features in the floral 

 axis, and we have here a particularly good case in point. 



SCHEUCHZERIA PALUSTRIS 



The rhizome of this monotypic genus bears a general resemblance 

 to that of Triglochin, but its tissues are much more lacunar, both in 

 the intra- and extra-stelar regions. The cortex lacks the mechanical 

 fibers found in Triglochin, and the island of such tissue is absent from 

 the stele. Numerous leaf traces enter the cortex from the sheathing 



r 



leaves; the larger traces penetrate directly into the interior of the stele, 

 while the smaller ones run down through the cortex for nearly the 

 length of an internode before entering the central cylinder. The 

 structure of the central cylinder of tho rhizome is shown in fg. 34; 

 leaf traces are to be seen in various stages of penetration in to the 

 cylinder. ]Most of the bundles lie in a circle at the outer border of the 

 stele, and it will be noticed that practically all of them are amphivasal, 

 although Chatin (4) figures them as collateral. It is probable that 

 his figure is from a higher region of the stem, for I have found that in 

 this region the bundles are more nearly collateral, i. e.,- with U-shaped 

 xylem. It is of interest to add that in the upper nodes the leaf traces 

 enter the stele through distinct gaps. The floral axis is strengthened 

 by a thick fibrous ring, inside which are collateral bundles arranged in 

 an irregular ring, with three or four lying a short distance farther in. 

 Thus the arrangement is not so simple as in Triglochin. 



The affinities of this and the preceding genus seem to be with 

 Alismaceae rather than Potamogetonaceae, hence no attempt will be 

 made at present to discuss this question. 



Relationships 



The view that the monocotyledons have been derived from the 

 dicotyledons has been put on a new foundation by recent anatomical 



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