PAPERS ON BOTANY 147 
a plant of entirely different aspect from the aquatic form. 
On these ponds it is that seasonal dimorphism reaches perhaps 
as great perfection as is found anywhere in the vegetable 
kingdom, in the ‘‘mud liverwort,” Riccia lutescens Schwein. 
The change of this plant from an elongate creeping thallus 
with inconspicuous slender rhizoids into a butterfly-shaped 
floating thallus, well furnished with conspicuous balancing 
scales and reproducing itself, much like an amoeba, by bi- 
partition, and the process of its change—all the heavier pos- 
terior portion sinking and dying while a newly developed 
spongy heart-shaped apical portion survives to develop into 
the floating form—is almost as remarkable as the metamor- 
phosis of a butterfly. The change is indeed so striking that 
even among good botanists this floating form is frequently, if 
not generally mistaken for an entirely different plant, the 
floating liverwort, Ricciocarpus natans L. and, to increase 
confusion, the just mentioned liverwort, which is never found 
in temporary bodies of water, but only in lakes, rather infre- 
quently produces a creeping form simulating the dry-pond 
stage of the mud liverwort. 
A more remarkable effect of the region along shore, how- 
ever, is the influence it exerts, not upon the members of its 
native flora, where great variability might naturally be ex- 
pected, but upon such plants as have strayed down from the 
neighboring uplands, plants which here suffer a modification, 
not in their form, but in their size. In many cases plants, 
which on their native uplands, reach to a respectable stature, 
here undergo such diminution that they often barely exceed 
some of the larger species of moss. This diminutive flora is 
likely to be almost or entirely overlooked during the general 
growing season, and attracts attention to itself only after the 
frosts of autumn have cut down the tender herbage of the 
surrounding country. After this has happened, the humble 
plants along shore, protected by their closeness to the warmer 
earth and adjacent water surface, remain still unscathed, their 
leaves retaining the verdure of summer, and their blossoms 
the brightness of their prime. Even at this season, when they 
show up at their best, they are an inconspicuous group, and 
are usually discovered only when looking for something else, 
such as pebbles or shells along shore. During the survey of 
the Lake Maxinkuckee region, the writer become tolerably 
