42 



SCIENCE-GOSSIP. 



CHARACTERISTIC BRAXCHIXG OF BRITISH FOREST-TREES. 



By THE Rev. W, H. Pcrchas. 

 {Continued from page i6.) 



The Birch. 



T N its early life, especially when vigorous, the 

 birch (Betida alba, Liim.) is often of bushy 

 growth, moderately stiff f\\'igs arising from each node 

 or joining, and showing little tendency to become 

 pendulous. Gradually, as the stem and branches 

 increase in length and as the twigs produced are 

 less thick and robust than at first, these latter 



Birch. Late Summer State. 



Barren Catkin for nest year. 



{a) Fenile Catkin enclosed in bud. 



assume more of the pendulous character which 

 gives so much elegance to the tree and which has 

 earned for it the title of " Lady of the Wood." 



The arrangement of the leaves in the birch is not 

 two-ranked as in the elm and beech, but is a spiral, 

 whose fourth leaf ranges over the first, and thus 

 each leaf and consequently its resulting leaf-bud or 

 shoot, diverges from its nearest neighbour, whether 

 above or below, at an angle of 120 degrees, i.e. one- 

 third of the circumference of the stem ; thus the 

 twigs or branches arise at more uniform angular 

 distances around the stem than where the arrange- 

 ment is two-ranked, although the internodes which 

 separate them is often considerable. 



As to the position of the flov.-ers. The birch is 

 monoecious, i.e. the staminate and pistillate flowers 

 are produced by the same indi\-idual tree, but 



grouped in separate catkins as in the beech. The 

 barren or staminate catkins are terminal, formed 

 towards the close of each summer at the tip of the 

 yearly shoot. They have no protecting bud-scales, 

 and they continue exposed through the winter ready 

 to expand in the following spring. At first sight 

 the catkin or group of catkins seems to be lateral 

 and opposite to the upper- 

 most leaf, but on exami- 

 nation it is seen that 

 although turned towards 

 one side it is really 

 terminal, its stalk being 

 the true continuation of 

 the axis. This turning 

 to one side allows the 

 uppermost axillary bud 

 to stand at the tip of the 

 shoot and to perform the 

 office of growing point ; 

 hence the shoot to which 

 it gives rise in the next 

 season is continuous in 

 direction w-ith the pre- 

 vious growths. 



The fertile or pistillate 

 catkins, on the other 

 hand, are lateral, and are 

 enclosed in axillary buds, 

 the scales of which do 

 not unfold and disclose 

 the young catkin to \-iew 

 until the follo\\-ing spring, 

 at which time the barren 

 catkins also open. These 

 winter-buds are formed in the axils of leaves some- 

 what low down the j-ear's shoot. 



The pistillate catkin, with its stalk, is really the 

 axis of a spur or short shoot w-ith undeveloped 

 internodes, as is seen by the two or three leaves at 

 the base of the catkin stalk. In the axil of one or 

 more of these leaves buds are formed which, in 

 another season, continue the growth of the spur 

 and produce other pistillate catkins. After some 

 seasons, however, these spurs gradually die off and 

 leave those portions of the branches bare. The 

 buds which give rise to leaf}" growth generally arise 

 from the axils of the upper leaves of the shoot, 

 and thus in the full-grown birch-the branches are 

 bare in their lower portion, but terminate in tufts 

 of lengthened drooping twigs. The angle which the 

 branches make with the parent stem or branch is 



