Roscndahl: symplocarpus and lysichiton. 145 



come blasted and that the leaves are less modified through eco- 

 logical adaptations. 



The root system of these two aroids is so remarkable that it 

 deserves at least a passing notice in this connection. 



The seeds germinate at or near the surface of the ground, 

 but the young rhizomes are soon pulled down into deeper layers 

 of the soil by the contractile roots. In Symplocarpus two and 

 three year old seedlings, often with the seed still attached, have 

 their short rhizomes 3-6 cm. deep in the ground. 



The roots are produced in very large numbers and cover 

 the rhizomes very thickly as can be seen in Figs. 3 and 5, Plate 

 XXII. The plant to the left in Fig. 3 has 132 roots by actual count 

 and those in Fig. 5 195 and 200 each. At first these roots are 

 smooth and perfectly white in color (Fig. 3). They soon as- 

 sume a yellowish brown color and begin to show characteristic 

 transverse furrows and ridges which indicate that they are short- 

 ening and exerting a downward pull upon the rhizome. The 

 greatest amount of contraction is in the upper part of the roots. 

 Their contractility can easily be demonstrated simply by pulling on 

 them until the furrows disappear. Upon being released they shorten 

 up again like a rubber band and become wrinkled. 



The rhizomes are of such large dimensions (2.5-5 cm. in 

 diameter), that even though the plants grow in moist ground 

 and mucky places, they offer great resistance to being forced 

 end downward into the soil. They encounter roots and under- 

 ground stems of other plants as well as pebbles, rocks, etc., and 

 old rhizomes show the effect of such resistance by the lower end 

 being worn perfectly smooth and having no traces of roots, leaf 

 scars and other inequalities of the surface (Plate XXII, Fig. 5). The 

 plants of Symplocarpus illustrated in Fig. 3 are both comparatively 

 young, the rhizomes having only within the last four or five years 

 attained their full diameter, and no wearing off is as yet per- 

 ceptible at the lower end. When too great an obstruction is met 

 the lower end becomes deflected and the stem will then assume 

 a more or less oblique instead of erect manner of growth. 



Relationship : According to Engler's classification Symplocar- 

 pus, Lysichiton and Oroiitiuin constitute the tribe Symplocarpeae 

 of the sub-family Calloideae. Only one more tribe, the Calleae, 

 consisting of the single monotypic genus Calla is included in the 



