1921] EMERSON—BOG PLANTS 365 
3 cm., and there are not more than three or four feeble, unbranched 
roots living at any time. Although a comparatively small plant, 
it appears to be able to grow upward rapidly enough to keep from 
being covered by the Sphagnum in which it often grows. 
Lathyrus palustris (fig. 6).—The rhizomes and roots are hori- 
zontal in this species, and were not found living below water. 
The rhizomes were mostly about 5 cm. deep. The roots were few 
in number, short, and only slightly branched. Those around the 
aerial stems had numerous large tubercles containing bacteria. 
Fic. 5.—Sarracenia purpurea, entire root system; stem and roots dead below 
depth of é cm.; roots in normal posi 
Decodon verticillatus—This species is the most prominent 
pioneer extending the floating mat out over the lake. Wherever 
the stems come in contact with water, large amounts of cortical 
aerenchyma form and numerous adventitious roots grow down. 
Considerable quantities of peat cling to this mass of stems and 
roots, and thus a floating substratum is formed on which other 
plants soon begin to grow. Among the most common of these are 
Sphagnum, Aspidium, and Scirpus. The greatest depth to which 
the roots of Decodon descend in the water was not determined 
accurately, but it was found that they attain at least a depth of 
more than 40 cm. 
