1907] CHRYSLER— POT AMOGETONACEAE 179 



its ovary might be derived from an ancestor of Zannichellia by the 

 suppression of all the carpels but one. 



Aponogetonaceae 



APONOGETON FENESTRALIS 



The creeping rhizome of this bizarre plant differs markedly from 

 those found in Potamogetonaceae, being much less lacunar and hav- 

 ing its cells loaded with starch. The vascular cylinder is poorly 

 defined^ since no endodermis is visible and the bundles are not numer- 

 ous. Some of these lie at what is to be regarded as the periphery of 

 the central cylinder, and a few others run in the medulla. \Qry few 

 of these are amphivasal, and all are weak looking strands with their 

 xylem hardly lignified. At intervals the peripheral bundles are con- 

 nected by a girdle of vascular strands, so that an almost complete 

 ring is formed. Seven or more traces enter from the sheathing base of 

 each leaf; rapidly traversing the cortex and penetrating to near the 

 middle of the stele, where they anastomose with one another and pro- 

 ceed downward through the medulla. Thus the vascular structure 

 resembles that of the majority of monocotyledons which have a creep- 

 ing rhizome much more than it does that of Potamogeton. In this 

 respect and in its floral characters the genus seems more closely related 

 to Alismaceae or Juncaginaceae than to the families so far discussed. 



Juncaginaceae 



TRIGLOCHITsT MARITIMA 



It is not intended to enter in any detail into the morphology of 

 this genus, but to call attention to certain features which seem of 

 theoretic interest. Contrary to the habit of the plants at the other end 

 of the series, Triglochin has a stocky subterranean stem with short 

 internodes, resembling Acorus and many of the sedges. Fig. 33 

 shows its central cylinder; an endodermis is visible, within which are 

 a number of bundles, mostly amphivasal, imbedded in fundamental 

 tissue which is not lacunar as is the cortex, but contains much starch. 

 In the center of the stele is an island of mechanical tissue. The 

 presence of amphivasal bundles throughout the length of the stele 

 easily distinguishes this genus from Potamogeton. The writer has 

 already (6) expressed the view that such bundles arising in the nodes 



