154 



Science). Perhaps no better illustration is needed to show that 

 anchorage is a chief end of a tree root system, and not pri- 

 marily to obtain a major amount of the plant food needed in 

 up-building trunk and branches. Here again the writer must 

 remark on the marvelous difference in the habitat of these 

 two trees from the swamp home of the one in Michigan and 

 the other in Massachusetts. 



The alluvium of all the streams of any size, and reaching 

 the greatest development along the Mississippi river, is the 

 chosen home of the last association to be discussed, the 

 elm-zvillow. As a matter of course, the soil is exceedingly rich 

 but often very wet, although rarely marshy, and subject to every 

 considerable overflow of the adjacent river. WJiite elms are 

 everywhere the common tree on the drier portions, assuming 

 magnificent proportions ( 100 feet high and with a diameter of 

 6 feet). On the moister lands the soft maple grows to immense 

 size, one specimen having a diameter of 7 feet. Near the water 

 the black and peach willows are common, and commonly are 

 the river bank trees. White and black ash are common, the 

 latter in genuine swamps. Here and there are clumps of giant 

 sycamores, that are the largest trees of the entire region. Where 

 alluvial soil disappears and sand begins, the sand-bar willow, 

 (Salix longifolia), is the dominant form, growing in dense 

 thickets, and serving as a catch-all for all the debris of the 

 great river, which debris is the beginning of the true bottoms. 



Associated with these trees are a number of herbaceous 

 plants that are characteristic. Among them we note Leersia 

 virginica and oryzoides, Cinna, Elymus, Polygonum of many 

 species, Impatieiis pallida and hlHora, Convolvulus sepium, Cus- 

 cuta of several species, Stachys palustris and aspera, Scutellaria 

 lateriflora, Chelone, Mimulus ringcns, Lobelia cardinalis, Helian- 

 thus, and Solidago. 



In concluding these words about the forest trees, it will be 

 advisable to mention a few species that may be called sporadic, 

 to use a medical term, that is a few of one species found in a 

 circumscribed locality, and perhaps no others known in the 

 whole district or separated by miles of intervening territory. 



