Lake Mqxinkuckee, Physical and Biological Survey 137 



Two more noteworthy instances occur to mind. At certain 

 places along shore there is found growing in the water a plant 

 which in leaf-form and general habit, resembles Potamogeton 

 iicdans, but which is really a smartweed bearing pretty spikes of 

 pink blossoms; and finally in the waters of the lake among the 

 pondweeds and milfoils one finds a most remarkable plant which 

 has whorls of dissected leaves and bears a considerable resemblance 

 to some sort of milfoil or a close resemblance to the aquatic form, 

 Cabomba. This plant upon blossoming and fruiting proves to be 

 a species of bur-marigold. 



It will occur at once to the reader that the region along the 

 shore-line is an excellent place to study evolutionary forces at work, 

 and the question of the possible relations between the shore plants 

 and the aquatics will at once arise. 



In the temporary woodland ponds the changes of form of plants 

 to suit conditions is much more striking, but not so deep-seated. 

 Here we have the remarkable water-parsnip, which in early spring 

 when the pond is full of water, is a rosette of purple; finely-dis- 

 sected leaves appear, but later as it shoots up, its stalk puts out 

 leaves more and more nearly entire as it approaches the water- 

 surface until the aerial leaves of the same plant that bore collaps- 

 ible submersed leaves below, are firm and almost entire. A water 

 crowfoot of the ponds changes the shape, texture, and general as- 

 pect of its leaves so much after the water dries that it looks like an 

 entirely different plant. And the woodland pond and the lake 

 edge each has its own species of Riccia that have parallel changes 

 and land forms entirely different from the floating form. 



A contemplation of these facts arouses speculation as to the 

 relationship and origin of the land and water floras. Conscious- 

 ness of the great adaptability which plants possess, and the recog- 

 nition of a greatly modified bur-marigold and smartweed among 

 the members of the water flora, cause us naturally to expect some 

 genetic relationship between the plants on land and those in the 

 lake. In this expectation we are disappointed. With the two ex- 

 ceptions given above, the aquatic plants belong not only to strictly 

 aquatic genera but usually also to strictly aquatic families and per- 

 haps orders. Zoological and botanical systems are so unlike that 

 it is impossible to make exact comparisons, but, generally speaking, 

 the plants of the lake are about as far removed in relationship from 

 the plants of the land as the fishes of the lake are from the animals 

 of the land. And yet we recognize among the plants tantalizing 

 similarities. 



The flowering plants of the lake evidently arose from terrestrial 



