230 



SCIEXCE-GOSSIP. 



CHARACTERISTIC BRANCHING OF BRITISH FOREST-TREES. 



By the Rev. W. H. Pcrchas. 



(continued from page 203.) 



The Sycamore. 



'THE leaves of the sycamore (Acer pseudo- 

 planianus) are opposite in pairs, each pair, as 

 in the ash-tree, standing at right angles to the pairs 

 next above and below. The internodes or spaces 

 of stem between the neighb During pairs of leaves 

 are shorter than in the ash, commonly about two 

 and a half or three inches in young trees and in 

 vigorously growing parts of older ones. The angle 

 at which the large branches come off from the 

 main stem varies considerably; in some cases, 

 especially in the 

 lower branches, 

 it is so large that 

 their direction is 

 almost horizon- 

 tal : in other cases 

 the branches are 

 found to ascend 

 at about an angle 

 of forty -five de- 

 grees, but the 

 secondary and 

 smaller branches 

 generally show a 

 tendency to turn 

 upward toward 

 the sky. The 

 branches are op- 

 posite in cros- 

 sing pairs, the 

 growing point, 

 whether of stem 

 or branch, con- 

 tinuing for a 

 series of years to 

 push forward in 

 the original di- 

 rection, opposite branchlets being thrown out at 

 almost everj- joint when the stem or branch is 

 vigorous, but where the growth is less active, 

 the buds at the lower part of each yearly shoot 

 will remain dormant, those only which are nearer 

 to the point giving rise to new branchlets. So 

 soon, however, as the flowering habit comes on 

 the mode of growth begins to be altered. The 

 inflorescence, which is alwaj-s at the extremity of a 

 short leafy shoot of about two joints (0), is produced 

 first on the small lateral branches, generally on 

 such as are third or fourth in order from the main 

 branches, and since the inflorescence is thus 

 terminal, no further lengthening of the shoot 



Sycamore, in Summer State. 



a, End of previous j ear's and junction with present years shoot 



b, Flower-bearing shoot of present year. c. c, Bods formed 



at base of inflorescence. 



which bears it is possible. The raceme falls off 

 when the seed is ripened, and leaves a clean scar ; 

 but a pair of buds (c , c) are formed in the axils of the 

 leaves which stood right and left of the point 

 whence the inflorescence originated. These in the 

 next season give rise to a pair of branchlets, form- 

 ing an angle with that from which the}- sprang ; 

 these again in their turn are tipped by buds which 

 in another season give rise to other pairs of branch- 

 lets. All these branchlets turn upwards towards 



the sky, and thus 

 the branch, if 

 horizontal, has a 

 level - topped 

 series of branch- 

 lets along great 

 part of its length ; 

 the main axil, 

 however, con- 

 tinues for a while 

 to push forward 

 in its original 

 direction. The 

 flowering tend- 

 enc\- extends it- 

 self more and 

 more towards the 

 point of the 

 branch, and by- 

 and-by affects the 

 leader itself of 

 the branch, a 

 cluster of flowers 

 being borne at 

 its termination. 

 From this time 

 forward its lead- 

 ership is at an end, being exchanged for the 

 growth of pairs of branchlets crossing each other 

 as to their point of origin, but tending upwards in 

 direction ; thus, instead of a single shoot at the 

 point of each branch, we have a bushy head of 

 spray wood, each main branch forming a compact 

 rounded head, the leaves of which closely approach 

 or overlap. Hence those bold rounded masses of 

 foliage which receive the fight and stand out apart 

 from each other relieved by deep shadows as we 

 look into the inner part of the tree. In winter too 

 this mode of growth is very observable. Each 

 branch is seen to terminate in a bushy mass of 

 intercrossing sprays of nearly equal length, thus 



