94 



SCIENCE-GOSSIP. 



CHARACTERISTIC BRANCHING OF BRITISH FOREST-TREES. 



The Alder. 

 'T^HE Alder (Alnus glutinosa, Gaertn.) is a tree of 

 moderate dimensions, often little more than a 

 bush, but in situations where the soil is tolerably 

 good, or when growing on river banks or in marshes, 

 it will attain a height of sixty feet and upwards. 



By THE Rev. W. H. Purchas. 



{Continued from page 72.) 



The angle at which the branches leave the trunk 

 is less than forty-five degrees, but they soon become 

 horizontal or deflexed by reason of their own 

 weight. In the ultimate sprays the smallness of 

 the angle which they make with each other is very 

 manifest. The length of the internode in vigorous, 



Alder (Alnus glutiitosa). 

 a, Emtryo pistillate catkins ; b, Embryo stamminate catkins. 



The leaf-arrangement is commonly such that the 

 cycle consists of three leaves, the fourth leaf 

 standing vertically over the first, the fifth over the 

 second, and so on. Thus the divergence of each 

 leaf from the next (as viewed from the centre of 

 the stem) is one-third of the circumference, 

 whence it follows that the branches which arise 

 from the axillary buds will stand more uniformly 

 around the stem or shoot than in the elm or lime, 

 where they are two-ranked. 



leafy shoots is some two inches or more, but in the 

 small flowering sprays it is only from one-eighth 

 to five-eighths of an inch. 



The group of catkins which constitutes the 

 inflorescence is terminal. The staminate and 

 pistillate flowers are borne in separate catkins. 

 The staminate or male catkins _are arranged in a 

 raceme or small panicle, springing from the point 

 itself of the branchlet, the pistillate or female 

 catkins, which are smaller and fewer in number, are 



