270 PHYSIOLOGICAL BOTANY. 



of the Birches. Beneath the epidermis a small heap of 

 cells, filled with green matter, is seen, and which is 

 slightly elevated above the surface ; it gradually becomes 

 larger, and lacerates the epidermis. More cells then 

 become superimposed upon each other, and form a capi- 

 tule, with a more or less thick pedicel formed by the 

 lower cells. The outer cells subsequently become wholly 

 converted into a resinous matter, and are surrounded 

 with a dense brittle mass, the pedicel still remaining 

 unaltered. Finally, the granules escape from the epider- 

 mis. The dense brittle mass dissolves in alcohol or ether, 

 forming a mucous mass, leaving no trace of any membrane 

 (which however might very easily be concealed in the 

 mucous mass). The author gives the chemical exami- 

 nation of betuline ; he considers it to be a kind of 

 stearoptine. 



LEAVES. 



Remarks upon the Arrangement of the Leaves in Dicoty- 

 ledons. By K. S. KUNTH. Bericht d. Akad. d. Wiss. z. 

 Berlin, October 1843. The position of the leaves coin- 

 cides with that of the buds, says the author, and when a 

 bud is about to be formed, a portion of the pith is forced 

 through the woody substance towards the surface of 

 the stem. The spot where this takes place depends upon 

 the arrangement of the woody bundles; thus the first 

 year's shoots of the oak are pentagonal, and the leaves are 

 also arranged in five ranks. On endeavouring to connect 

 the leaves by a line in the shortest course, this can only be 

 done in a spiral direction, and from left to right ; more- 

 over the spiral line, to be enabled to reach the nearest 

 leaf, must pass over one of the angles of the wood, to 

 arrive at a leaf which belongs to the same series. Five 

 angles are not always present, still five divisions of the 

 wood may always be assumed to exist when the leaves 

 are arranged in this manner. The author next refers the 

 arrangement of the leaves in the shoots of Castanea vesca 



