Populus Salicaceae 353 



Tips of the branchlets not curved upward (in winter phase); mature leaves ovate, 



broadly ovate to nearly orbicular, mostly less than 8 cm wide (except those of 



root and coppice shoots); stamens 6-12; capsules 1.5-3 mm in diameter. 



Winter buds more or less pubescent, dull; young branchlets gray-tomentose at 



first; leaves generally with less than 12 teeth on each side (except those of 



root shoots) 5. P.. grandidentata. 



Winter buds glabrous, glossy; young branchlets glabrous or nearly so at first; 

 leaves mostly with more than 12 teeth on each side 6. P. tremuloides. 



1. Populus alba L. White Poplar. This species has been freely 

 planted throughout the state and has escaped in all parts. It rapidly 

 spreads from root shoots, and, when not restricted, it soon spreads in all 

 directions, in fields and woodland in all kinds of soils except very wet ones. 

 It is no longer planted by anyone familiar with its habit of spreading or 

 one who knows that the branches are killed by the oyster-shell scale. 



Nat. of Eurasia. 



2. Populus heterophylla L. Swamp Cottonwood. Map 729. In Indiana 

 it is infrequent in the lake area, local in the central part, local to frequent 

 in the southern part, and possibly absent in the southeastern part. It be- 

 comes a tall, slender tree, 10-16 inches in diameter. It grows on the borders 

 of ponds in woodlands which have for a subsoil a stiff blue clay, locally 

 called "gumbo." The habitat simulates that of pin oak but I do not recall 

 ever seeing these species growing together. It is usually associated with 

 red maple, sweet gum, and cypress. Where there are more than a few trees 

 it is usually found in a pure stand. It is most abundant in the sloughs of 

 the Lower Wabash Bottoms. 



Atlantic coast from Conn, to Fla., westw. to La., and northw. in the 

 Mississippi Valley to n. Ohio, s. Mich., and Mo. 



3. Populus Tacamahacca Mill. (Populus balsamifera of some recent 

 authors.) Balsam Poplar. A few colonies of this poplar have been found 

 along Lake Michigan in Lake, Porter, and La Porte Counties, and it has 

 been found in St. Joseph County. The trees I have seen are small ones 

 near the lake front. 



Newf. and Lab. to Alaska, southw. and reaching the U. S. only on 

 the northern border. 



3a. Populus Tacamahacca var. candicans (Ait.) Stout. (Populus candi- 

 cans Ait.) See Jour. N. Y. Bot. Gard. 30: 25-37. 1929. This variety is 

 found in the eastern part of the range of the species and is found as a 

 small tree along Lake Michigan. The clon, Balm of Gilead, originating 

 from a specimen of this variety, has been freely planted but I do not know 

 of any place where it is spreading. 



4. Populus deltoides Michx. Cottonwood. Map 730. This is one of the 

 largest trees of the state and is found throughout. It grows only in low 

 ground about ponds, in woodland, and along streams and ditches. 



N. H., w. Que. to the Rocky Mts., southw. to Fla. and Tex. 



