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THE WILD CHERRY (PRUNUS AVIUM). 



P. O. KEEGAN, LL.D., 

 Pattefdale, Westmorland. 



As this tree may in many respects be regarded as one of the 

 glories of the Lake District, I have considered that a kind of 

 monograph of its chief structural and physiological peculiarities 

 would be presentable and of some interest. In the first place, 

 it will hardly be necessary to dwell upon the general descriptive 

 features, systematic affinities, and so on, as these must be 

 abundantly familiar to all students of botanical science. 

 I propose, therefore, to pass in successive review the axial 

 organs (stem, root, etc.), then the foliar organs (leaves), and 

 lastly, the reproductive organs (flower, fruit). 



Stem and Root. — The wood of the stem is hard, heavy 

 (specific gravity 0*579 to 0*785), and tenacious, with a white, 

 distinct, slightly thick alburnum, and a clear brownish-red 

 duramen. The following histological features are presented : — 

 The vessels are small and narrow (about 40 micro-mm. average 

 diameter) and with the strongly-thickened fibres are grouped 

 partly isolated and partly irregularly throughout the entire 

 annual layer, but the former are larger and more numerous 

 in the (inner) spring wood ; parenchyma occurs beside the 

 vessels and between the fibres in the spring wood, but is 

 rather scanty ; the medullary rays as seen on the tangential 

 section are long pointed spindles (about 60 rays in a square 

 mm.) ten to twelve cell-layers high and up to six layers wide, 

 the cells being rectangular, thick-walled, porous, and radially 

 extended. The bark exhibits a very remarkable structure ; 

 the cambium is not sharply or clearly defined, and it is pierced 

 by the medullary rays which continue uninterruptedly into the 

 bast as white tough bands with cells not so stout ; what may 

 be called the ground-mass of the bast-layer is formed of what 

 has been termed ' hornbast,' i.e., the walls of its cells have 

 grown and thickened so very rapidly that, in default of space, 

 they become folded in a wavy shape and at the same time 

 their cell-space is contracted so as to assume a stellate shape, 

 or at times appearing as a labyrinthine or serpentine line, the 

 whole forming an apparently homogeneous mass interspersed 

 with fine wavy lines as in horn ; in this ground-mass lie the 

 bast-fibres which, especially in the young bast, form concentric 

 zones lying at fixed distances apart, also bast-parenchyma 



1900 July 2. 



