STUDIES OF LEAF AND TREE (PART II.) 



97 



In a brief article, with instructive illustrations, the hybrids of our oaks 

 are beautifully presented in American Forestry for November, 1917, by 

 Mr. George B. Sudworth, who covers the subject quite fully for a new sub- 

 species, and throws much light on the hybridization of these trees in general. 

 Oaks are the only trees now in existence in the world the fruit of which 

 takes the form of an acorn ; while so characteristic are their leaves that nearly 

 everyone can distinguish any kind of an oak leaf the moment he sees it. Most 

 oaks are a quarter of a century old or rather less before they begin to bear 

 acorns ; but they all produce these in due time no known species being lack- 

 ing in this particular. The general characters of oak leaves, with respect to 

 form, are well shown in a number of the figures of the present article, a suf- 

 ficient array having been selected in that their variations may be advantageously 

 studied. Their sinuses will be seen to vary widely owing to the differences 

 in their lobing (Compare figures 23 and 24). Dendrologists, or scientific 

 students and describers of trees, have 

 listed over three hundred different 

 kinds of oaks, and no doubt many 

 new ones will be described by bot- 

 anists of the future. 



With respect to the distribution of 

 oaks, it may be said that the trees of 

 this genus flourish throughout exten- 

 sive areas from one end of the North- 

 ern Hemisphere to the other. In Cen- 

 tral America various species carry this 

 distribution to the Equator; and here 

 they cross on the mountainous ranges, 

 to occur down through the Andes for 

 some considerable distance. In all 

 these countries, the wood of most of 



UNDER VIEW OF A TYPICAL LEAF OF THE 

 SCARLET OAK (Quercus coccinea). DISTRICT 

 OF COLUMBIA SPECIMEN 



Fig. 23 This average example is useful when one 

 comes to study the leaves of this species with the 

 view of considering the great number of varia- 

 tions these leaves offer the student. 



GREAT VARIATION' IN THE LEAVES OF 

 THE PIN OAK (Q. palustris); UNDER SIDES 



Fig. 26 It would probably require several hun- 

 dred fully matured leaves of. this species of oak 

 in order to exhibit the extraordinary number of 

 outlines they may present. 



the oaks, if not of all, is held in high 

 esteem for its durability and strength 

 few products of the kind equaling 

 it commercially. 



There are said to be upwards of 

 fifty species of oaks described for 

 this country, the forms on the At- 

 lantic and Pacific sides being quite 

 different ; the indigenous species are 

 restricted to their original areas of 

 distribution, unless collected therein 

 by man and planted elsewhere. 



A good example of oak flowers is 

 here shown in Fig. 30, which is sure- 

 ly an interesting and graceful dis- 

 play. These are the staminate flowers, 

 while the clusters of the pistillate ones are few in number, and are to be 

 found in the leaf-axils. 



Apart from Pasania of Oregon and California (P. densiflora), the com- 

 mon tan-bark oak of the Pacific coast, the remainder of the United States 

 species are. usually divided into two groups, both falling within the genu? 

 Quercus; these are known as the White Oak group and the Black Oak 

 group. In the case of the first, of which the White Oak {Quercus alba) i; 

 the type, the bark is very pale colored, and the leaves have rounded lobes 

 and sinuses. In the Black Oak group the bark is always dark-colored, and 

 the leaves, or rather their lobes, are sharp-pointed, the points terminating in 

 sharp little prickles, as in Q. velutina. All the White Oaks are annual- 

 fruited, and all the Black Oaks biennial-fruited. Gray tells us that "all the 

 species incline to hybridize freely." 



As all good foresters know, one of our grandest oaks is the Scarlet oak 

 (Q. coccinea), a fine example of which is here given in Fig. 19; variations 

 in its leaves are shown in Figures 20 (lower one) and 23 (typical). The 



VARIATION IN THE LEAVES OF THE POST 

 OAK (Quercus slellata); UNDER SIDES. WASH- 

 INGTON, D. C. 



Fig 24 As in the case of all oaks, the leaves of 

 this species vary in outline quite as often as any 

 other; so great is it sometimes that correct iden- 

 tification becomes quite puzzling. 



