92 RELATION OF PHYLLOTAXIS TO MECHANICAL LAWS. 



right- and left-hand spirals should be approximately equally dis- 

 tributed among them.* 



* Bonnet (loc. cit., p. 179) gives 43 Right and 30 Left as the result of the 

 examination of 73 Chicory plants, or 59 : 41 per cent. 



Observations on Pine cones do not yield very conclusive results, thus : — 

 I. 100 cones from one tree of Finns austriaca (B.G.O. 1900) were counted ; 

 the curves on the base of the dry expanded cone are (8 + 13), the 

 direction of one of the shorter (13) curves is readily checked : 

 comparison of the table (fig. 34) shows that in such a system the 

 genetic-spiral winds in the same direction as the long curves. As the 

 cone is viewed from below, the spiral of the diagram will be the reverse, 

 or the same as that of the short curves observed. Such a set of cones 

 gave 59 Eight and 41 Left. 

 II. 100 cones from one tree of Pinus pumilio (B.G.O. 1900) showing similar 



construction gave 53 Right and 47 Left. 

 III. 100 cones from one tree of Pinus laricio (E. G. Broome, 1900), the " 8 " 



curves being marked gave 68 Left and 32 Right. 

 The inequality of these numbers may therefore be the expression of the fact 

 that homodromy is more usual than heterodromy, and further observations are 

 needed. 



These have been made for the same trees by Mr E. G. Broome for 1901 with 

 closely similar results : — 1000 cones from the same tree of P. austriaca gave in 

 batches of 100 each — 



L. 

 46 



: 44 



49 



: 51 



R. 



54 : 

 56 

 51 : 

 49 

 54 : 46 

 57 : 43 

 54 : 46 

 56 : 44 

 51 : 49 

 54 : 46 



(1) 

 (2) 

 (3) 

 (4) 

 (5) 

 (6) 

 (7) 

 (8) 

 (9) 

 (10) 



R. 

 Average 53"6 



L. 

 46-4 



Although very nearly equal, there was thus a distinct tendency in this tree 

 to form a right-hand spiral. 



The case of the specimen of P. laricio was even more remarkable. 



Pour hundred cones were counted ; 

 with that of the previoiLS year. 



the first hundred gave a result identical 



32 



'75 : 25 



79 : 21 



.63 : 37 



Or an average of 71 Left : 39 Right, a result in which the element of chance 

 appears quite out of the question, so far as the members of one tree are concerned. 



Successive batches of 100 each. 



