1909] 



STOKEY— ANATOMY OF ISOETES 333 



Summary 



,. The vascular axis is a non-medullated monostele, composed of 

 tracheids and parenchyma. There is no differentiation into protoxy- 



lem and metaxylem. . , . « 



,. There is no primary phloem in the stem. It is found in the 



leaf traces and root bundles only. 



3. The cambium gives rise to cortex on the outside and secondan 

 dem on the inside. The so-called "prismatic layer" is secondary 

 xvlera. The cambium does not form phloem. 

 ' 4. The secondary xvlem consists of various combinations oi me 

 following types of cells: (a) Spiral and annular tracheids. (ft) mm 

 toe tracheids, slightly lignified, with irregular rings or spiral tnic c 

 ings. (c) Immature tracheids, magnified, nucleate or enucleate, 

 with irregular rings or spiral thickenings, (d) Immature tracne.*, 

 nucleate or enucleate, with slightly thickened, pitted walls. U 

 enchvma cells, which may have little protoplasm and small nuc ei, 

 abundant protoplasm and large nuclei. 



5- The secondary xvlem of /. Nuttallii shows zonation. J.«» 

 tpora var. Flettii and I. Tuckermani var. Harveyi do not. . 

 Poda shows it occasionally in old stems. Starch do * ^' ^j 

 secondary xvlem except in the parenchyma zones of i. ' 



6. The root bundles are collateral and monarch. lne P ^ 

 is found on the side away from the phloem and toward the cc 



st em, i. c, it is endarch. ,™rpntric in 



7. The leaf traces are collateral, but tend to become «*** 



the middle and upper part of the leaf. Thy xvlem P°^ on ^^ 

 great reduction above the sporangium, but the phloem is n 

 correspondingly. The sieve plates are transverse differentia . 



8. Near the vascular axis the leaf trace does not sno ^ ^ ^^ 

 tio n into protoxylem and metaxylem. In the outer P*"^ ]n ; 

 and in the region of the sporangium it is usual y ex ^ ^ 



X*mii it is occasionally mesarch above the sporan e iu 





re gion of the sporangium. 



This investigation was conducted at the University Q ^ _ 

 ,J nder the direction of Professor John M. Coulter a 



