52 



Proceedings of the Royal Irish Academij. 



of the diameters at the corresponding parts. (1) The diameters of the 

 branches in the young colony are equal to, and, in some cases, greater than, 

 corresponding measurements in tlie older colonies. The series of measure- 

 ments of twelve specimens given in Table C shows that (1) the length of the 

 main stem varies very little ; (2) there is a distinct tendency towards an 

 increase of length in the younger- branches and twigs in the older specimens. 



Table C. 



In Table C we have sought to analyse the nature of the constitution of 

 the diameter — in other words, to find the actual proportion of axis and 

 coenenchyma ; and here several very interesting and useful facts ha\e come 

 to light. 



(1) The thickness of the coenenchyma at the tip of the twigs is almost 



a constant ; in reality it is slightly thicker in the smaller specimens. 

 It is noteworthy that the diameter of the axis at this part is 

 negligible, being of a hair-like fineness. 



(2) Although the total diameter of branches lower down is greater than 



in the twigs, the actual thickness of the coenenchyma is never 

 greater, aa4,-iu some cases, is actually less. 



