94 
PROFESSOR W. 0. WILLIAMSON ON THE ORGANISATION 
sections of stems and branches of various ages and sizes, are given in the following 
table ;— 
Cabinet numbers of 
the slides contain¬ 
ing the specimens 
NvTmber of the vascular 
laminae in the 
1 
1 
examined. 
Inner margin. 
Outer margin. 
1 
Slide A. 1885 0. 
44 
54 
Central axial bundle dissociating 
„ B. 1885 A. 
46 
66 
Central axis solid, fig. 10 t 
„ C. 1883 A. 
58 
93 
Central axis solid i 
„ D. 1885 A. 
61 
96 
Central axis solid 
„ E. 1883 
62 
95 
Central axis solid. Brancb not yet emerged 
from the parent stem 
„ F. 1885 D. 
65 
89 
Specimen a corticated independent brancb 
„ G. 1141 
71 
85 
Specimen with a central medulla, fig. 12 
„ H. 1885 H. 
74 
97 
Central axis dissociating, fig. 11 
1. 1885 
78 
99 
Central axis solid 
„ K. 1884 
84 
139 
Independent corticated brancb, medulla mucb 
enlarged 1 
„ L. 1885 F. 
95 
150 
Independent corticated brancb, witb a medulla ’ 
„ M. 1138 
116 
200 
Independent brancb, medulla large 
„ N. 1885 
135 
233 
Independent brancb on stem 
„ 0. 1885 
272 
499 
„ P. 1128 
364 
642 
Tbe specimen represented in tbe outline, fig. 13 
„ Q. 131 
1120 
5460 
The above table shows that as each stem or branch increased in size, an increase also 
took place in the number of the radiating laminae that originated close to the raednllaiy 
border of the exogenous zone, as well as of those which reached its cortical margin. 
We find that the eight very young sections, A, B, C, D, E, G, H, I, had a mean 
number of 69 such protoxyloid laminae, whilst the seven larger branches, F, K, L, M, 
N, O, P, all of which had become independent or corticated branches, completely 
emerged from the parent cortex, had a mean of 161 such laminae, the example P 
having 364. The very large stem Q shows even a much further increase, having 1120 
of these primary laminae. That the second column should show a large number of 
secondary laminae intercalated between the periphery of the medulla and the inner¬ 
most cortex w'as to be expected where an exogenous mode of growth had obviously 
existed. 
It is clear thart many of the laminae thus indisputably added even to the inner 
border of the vascular zone, must have been intercalated chiefly in the intervals corre¬ 
sponding to a", a", of fig. 13 ; and it is perfectly clear that wherever they were 
developed along tins expanding medullary margin they must have pushed apart the 
older lamellae between winch they were so intercailated. Since every one of the larger 
and older branches in the lower half of my table must once have been small and young, 
like those of the upper half, it seems indisputable that we have here a phenomenon of 
growth and expansion wdiich has no parallel, that I am a’ware of, amongst living 
