Keegan: The Birch Tree. 207 
at the blade form a V, the system is therefore ‘ open,’ whereas 
in Alder and Hazel it is ‘closed.’ On 4th August, the leaves 
had 58 per cent. of water, and the dried substance contained 
3 per cent. wax and resin with a little carotin, some palmitic 
acid, and traces of volatile oil, 11 albumenoids, 4.3 tannin and 
quercitrin, considerable glucose and starch, a large quantity 
of pectosic mucilage with tartrate and oxalate of calcium (mostly 
in the lacunar tissue), and 3.5 ash which had 34 per cent. soluble 
salts, 4 silica, 25.3 lime, 8.4 magnesia, 11.3 P2O° and 4.4 SO3. 
The ash of the yellow and red autumn leaves rose to 5.8 per 
‘cent., and contained 6.9 per cent. silica, 39.8 lime, and 1.4 P?O®%. 
The chlorophyll of the leaf is disorganised about mid October ; 
but the nerves and parenchyma still retain considerable starch 
much later on. The resin glands of the young leaf become less 
active in September, and completely dry up in October. 
Flower and Fruit.—The inflorescence is in the form of catkins, 
the male flower being terminal, entirely naked, and born from a 
bud of the previous year, while the female flower is axillary, and 
springs from a bud of the current year, formed of five or six 
membranous scales, and borne on a lateral peduncle. At the 
time of fertilization in the female catkin there is visible only a 
single rounded scale, bearing at its base six pistils; there is 
no sign of a placenta or of ovules. Later on these pistils unite, 
and at maturity of the organ there is seen three bilocular carpels 
monosperm by abortion. ‘The fruit is a flattened samara with a 
membranous and transparent wing at each side. The seed is 
anatrope (the nucellus straight, and the chalaza distant from the 
hilum), without raphe, and pendulous ; the cotyledons are flat, 
and there is no endosperm ; it ripens in October, but the ger- 
minative capacity is lost in about six months. According to 
Jahne, the fruit (shell and seed) contains 10.5 per cent. water, 
18.2 fatty matter, 14.4 albumenoids, 11.4 sugar and dextrin, 
27.2 fibre, and 4.2 ash which (pure) has 27 per cent. potass, 
9g silica, 23.7 lime, 9.2 magnesia, 10.9 P?O% and 4.8 SO8. The 
reserve materials are aleurone and oil only, no starch. The 
Birch is a pretty prolific seed-producer, but few of our native 
trees generate more seed that is sterile, only about 20 per cent. 
thereof being fit to germinate. 
Physiological Summary.—A study of the chemical changes 
occurring in the Birch leaf during its life, teaches that the vege- 
tation of this tree so far approaches perfection. There is no 
serious decrease in the production of starch, cellulose, or lignin, 
the albumenoids and sugars diminish considerably in autumn, 
while there is no special or heavy fixation of insoluble matters 
1907 June 1, 
