1921] EMERSON—BOG PLANTS 361 
to scale on coordinate ruled paper (figs. 1, 3, 4, 6). In this work 
_ it soon became evident that, with the exception of a few species, 
living plant parts were very rare below a certain comparatively 
slight depth, and that each species had its own characteristic 
range of depths. In most cases the roots and rhizomes maintained 
almost the same level throughout their length. Hence in mapping 
it was necessary to show only the horizontal arrangement of the 
organs in question, stating the depth from the surface or the 
relation to the water table. Since the mat is held up by its own 
buoyancy, the surface remained at practically the same level 
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50 cm. - 
Fic. 1.—Aspidium Thelypteris, map of rhizome system: L, living attachment to 
older part of system; D, dead tips of rhizomes; F, foliage leaves; solid black lines, 
ving rhizomes; note numerous dead rhizome tips, represented by cross lines on 
white ground, in older parts; dying behind the dichotomous branches leaving them 
independent is a very common means of multiplication in this fern; depth 4-6 cm. 
throughout its extent and throughout the growing season. This 
distance from soil surface to water table was approximately 6 cm. 
As may be noted in the maps, the underground parts of bog plants 
are remarkably straight when compared with those of upland plants. 
oubtless this is largely because of the lack of mechanical inter- 
ference to the growing parts by the spongy peat. The more impor- 
tant species represented in this bog are as follows. 
Sphagnum.—This plant grows abundantly over most of the 
floating mat, especially toward the lakeward margin. It was 
found to be propagating vegetatively by growing above and 
dying. below. No other means of propagation was found. It 
appeared to remain alive to a depth of 3-4 cm. 
