THE ANATOMY OF ISOETES 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 126 



Alma G. Stokey 



(WITH PLATES XIX— XXI) 



There is no group of plants among ptcridophytes whose anatomy 

 has occasioned so much discussion as the genus Isoetes. The most 

 recent writers, Farmer on I. lacustris, R. Wilson Smith on L 

 tchinospora, and Scott and Hill on I. Hystrix, disagree in many 

 point. In view of the lack of harmony, both of observation and 

 interpretation, it has seemed advisable to make a comparative mvesti- 



I / 



gation of the anatomy of several American species. 



Historical 



The literature on the anatomy of Isoetes began in 1840 with a 

 paper by von Mohl (24). Although he recognized the lycopo 

 affinities of Isoetes, he noted several important points of difference, 

 in the arrangement and structure of the roots, and in the nature ot t e 

 cambium products. Ever since that day the question of the nature 

 of the cambium activity has afforded a fertile field for discussion and 

 " Is with that subject that this paper is chiefly concerned, VO» 

 Mohl regarded the whole of the secondary growth as parenchymatous- 

 and states that, as in other vascular crvptogams, there is no ***** 

 ^ thickness of the wood. The next significant work was that 

 Hofm„st E r ( l6 ) in ,857. In discussing the cambium goArt^ 

 says (p. 361): "The effect of the yearly renovation ot tne^ 

 "l* is not only to increase and renew the cortical tissue 



e 



ambial 

 but new 



,a >'er is not only to increase and renew the cortical tissue di 

 W cells also become added, although only sparingly, to the 



of the 



and 



of old vigorous plants. t 



1 1*0 or three cambium cells from the older V^^^° 



*"*> often exhibit thickenings of the walls, which by their delica cy 

 want of color betray their undoubted recent origin. ' 



appeared Russow's Vergleichende Unlersuchungen der Ui > 



Kr }'ptogamen (18), with a discussion of the anatomy of IJaCUS [[; n 

 hi »os P ora, and /. Hystrix. This paper has had great «*"« 

 Sequent work, and'to Russow's work may be attributed he c 



»il I Botanical Gazette, vol. 47 



