314 BOTANICAL GAZETTE ' (april 



very long, moderately stout leaves. It grows in inundated field- 

 and shallow ponds, where it is emersed during most of the summer. 

 /. Niittallii has a three-lobed trunk and long, very slender leaves. It 

 never grows under water, but near springs or springy places, and on 

 low wet grounds or meadows, where the ground becomes very dry in 

 the latter part of the season. 



Investigation 



The complicated structure and arrangement of the old stem is mow 

 easily understood by a study of the sporelings. The stem of a spore- 

 ling is a mass of undifferentiated parenchyma, traversed by leaf 

 traces, which come together to form the short flat stem plate an 



continue outward and downward into the roots. All observers 

 agree that in the young plants there is no cauline portion in the -torn 

 bundle, but whether or not there is a cauline portion in the older 

 stems has long been a disputed point. Hofmeister, de Bam 

 Campbell, and Farmer look upon the stem bundle as being made 

 up of leaf traces; while Hegelmaier, Bruchmann, and Scott an 

 Hill maintain that there is a cauline portion. In the short and com 

 pact stem there are no indications of a procambial strand, and a 

 there are never any tracheids present above the last leaf trace, 

 evidences of a cauline portion are not satisfactory. In following 

 cross-sections of leaf traces in a series of longitudinal sections up o 

 the place where the traces coalesce, it is easily seen that there is 

 sufficient amount of trachearv tissue in the leaf traces to account : 

 all the xylem in the stem bundle. Scott raised the objection t ^ 

 the tracheids of the stem are unlike those of the leaves, but there B 

 greater difference between the tracheids of the stem and of the M# 

 the leaf, than between those of the base of the leaf and of the u ?P*,!g^ 

 The difference is chiefly one of length, and this, together m th ^ 

 ences in the distribution of the thickening of the walls is corrc , 

 with the rate of growth of the part in which the tracheids are ^ ^ 



In all plants there is a separation into root and stem region- 

 this becomes more marked as the plant enlarges. A nis> s bb ^ 

 the tuberous body is not wholly stem, but a contracted stem ^^ 

 root. Owing to the compact growth and the consequent disp^ ^^ 

 of tissues, some of the root bundles in an old plant may be foun 



