50 



Proceedings of the Royal Irish Academy. 



The distance between branchings, though not constant, seems to increase 

 from the base upwards, so that the longest unbi-anched parts are the 

 terminal twigs. This is more marked in the taller colonies. In young dwarf 

 specimens the relative distances between the origin of the several branches 

 in ascending order is less pronounced, and the branches themselves are pro- 

 portionately thicker. Tliese- latter specimens therefore have a diflerent 

 appearance from the older and more elongated colonies, but must be ranked 

 in this species when we take into consideration the mode of growth, which 

 will be discussed later. 



Before doing so, however, it will be well to tabulate corresponding 

 measurements in individual colonies, and see how far these give us a clue to 

 the mode of growth. Fortunately we have in our possession intermediate 

 stages which show the different developments during growth from the 

 shortest to the tallest. 



The following tables may serve to form a basis for such a study. In 

 Table A the measurements ai-e all given in centimetres. The symbol + indi- 

 cates that the exact length is not known, owing to the basis of attachment 

 having been broken off. 



Tajble a. 



Figures 15, 16, and 17 show the branching in the colonies, which have 



been proportionately reduced. The largest (lig. 10) was 800 mm. in length. 



Let us consider two colonies which in general build are quite unlike one 



