334 FOREST TREES OF THE PACIFIC SLOPE. 



Family PLATANACEiE. 



A small group of trees characterized by large deciduous leaves and especially 

 by their minute flowers, borne in closely . packed, spherical or ball-like heads, 

 attached to a thread-like, pendulous stem. From one to half a dozen of these 

 ball-like, greenish clusters are produced on a stem. The male and female flowers 

 (each in ball-like clusters) occur, on different parts of the same tree, usually on 

 different parts of the same branch. The male clusters are smaller (about one- 

 third of an inch in diameter)" than the female heads (about one-half inch in 

 diameter). The female clusters develop into very characteristic, spherical, 

 hard balls of seed, the mature balls being from three-fourths inch to 1J inches 

 in diameter, one to six of which may be attached to a single pendent stem 

 (fig. 150). 



PLATANUS. SYCAMORES. 



The sycamores are a small group, the members of which are strikingly alike 

 in general appearance. Their most distinctive characteristic is the very thin, 

 smooth, whitish or pale green bark on young trunks and on the large branches 

 of old trees. Thin, veneer-like sheets of the bark are annually shed as a result 

 of the diameter growth of the stems. When exposed in this way the inner bark 

 is pale olive green at first and later a chalky white. All of the members of this 

 genus have this characteristic, which gives them a similar appearance. Differ- 

 ences in the lobing of the leaves and the amount of hair on their under sur- 

 faces, the number of fruit balls, and the shape of the seed (fruit) are depended 

 upon to distinguish the different species. The winter buds of sycamores are 

 also very characteristic. They are inclosed by the hollow bases of leaves, which 

 fit over them like a minute clown's cap, and when these leaves break away and 

 fall a circle is formed around the base of the conical bud, which is enveloped by 

 three cap-like scales. The balls of fruit are composed of long, slender, seed-like 

 bodies, densely packed together in a spherical mass. One end of the seeds is 

 attached to a central bullet-like body, from which they all radiate, side by side, 

 their opposite ends forming the surface of the sphere. A circle of fine, tawny, 

 stiff hairs is attached to the base of each seed (fruit). These heads, ripe in 

 late autumn, usually remain attached to the branches during the winter ; in the 

 spring they break up and the hairs about each seed (fruit) spread out, after 

 the manner of the silky hairs on a dandelion seed, adding greatly to the buoy- 

 ancy of the seed. As a result the seeds are easily and widely distributed by 

 the wind. 



The pale brown, reddish-tinged wood, very similar in all of these trees, is 

 characteristically marked by wide medullary or pith rays, most conspicuously 

 shown in quarter-sawed or radially cut sections. The wood is, moreover, pecul- 

 iarly " cross-grained," and on this account exceedingly difficult to split. Com- 

 mercially it is of rather secondary importance, but is attractive and suitable 

 for interior finish and cabinet work. The western sycamores are of little im- 

 portance, except to form protective growtbs along streams in dry. arid regions. 



Three species inhabit the United States and adjacent portions of Mexico, but 

 only one is found within the Pacific region, extending into Lower California. 

 Another species ranges through our Southwest into Mexico. The third is widely 

 distributed in the eastern United States. 



The sycamores are of ancient origin. Species now extinct, but very like our 

 eastern and the present European sycamores, were once common in Greenland 

 and in our Arctic region during the Cretaceous and Tertiary epochs ; they 

 existed also in middle Europe during the latter period, but became extinct when 

 that period ended. During the Tertiary epoch a number of sycamores, now 

 extinct, once existed in the central part of this continent. 



