Mexican Cottonwood 



175 



March, the catkins then being about 5 cm. long, the staminate ones densely 

 flowered; the scales are fringed with fiUform lobes; the stalks of the pistillate 

 flowers are very short, the disks dilated and rather large, the ovary smooth. In 

 ripening the pistillate catkins elongate to 10 cm. or more, the ovoid bluntish 

 capsules become 8 to 12 mm. long and much longer than their stalks. 



The wood is soft, light brown, and weak, with a specific gravity of about 0.48. 



II. MEXICAN COTTONWOOD — Populus mexicana Wesmffil 



The Mexican cottonwood has been confused with Fremont's cotton wood, to 

 which it is very closely related. It inhabits the banks of streams and rivers in 

 northern Mexico, extending northward into New Mexico and Arizona; it is not 

 known to occur in California. 

 The tree is round-topped, with 

 spreading branches, and reaches 

 a maximum height of 25 meters 

 or more, with a trunk some- 

 times 1.5 meters in diameter. 



The bark is light gray, that 

 of old trunks thick and ridged, 

 at least near the base, that of 

 young trees much thinner and 

 smooth. The young twigs are 

 greenish gray, hairy, soon be- 

 coming smooth and pale orange 

 to orange-brown. The buds 

 are orange-brown, finely hairy, 

 6 to 10 mm. long, pointed. The 

 leaves are broadly rhombic- 

 ovate to nearly triangular-ovate, 

 the base broadly wedge-shaped 

 or truncate, the apex usually 

 long-pointed; they are coarsely 

 and bhmtly toothed, firm in 

 texture, quite hairy when unfolding but smooth when mature, the upper side light 

 green and shining; the leaf-stalks are only a httle flattened sideways, and as long 

 as the blades, or shorter. The ovate hairy stipules are pointed and about 7 mm. 

 long. The tree flowers in February or March, with catkins about 6 cm. long; 

 the staminate catkins are densely flowered and over i cm. thick; the pistillate 

 flowers are short-stalked, the blunt ovary subtended by a cup-shaped disk 6 to 8 

 mm. wide. The ripe pistillate catkins are 10 cm. long or more, the stalks of the 

 flowers elongating to 4 or 5 mm., the capsule ovoid, blunt, about 8 mm. long. 



The tree has been much planted in cities and towns within its range. 



Fig. 132. — Mexican Cottonwood. 



