in the G ernes Primula. 
323 
Structure of the Apex. 
I found that in the apical region of these plants the vascular 
system undergoes no simplification whatever, but presents 
precisely the same arrangement as it does in the fully 
differentiated stem. Therefore, if in the fully differentiated 
regions there are several steles arranged in a slightly inter- 
rupted ring, as in P. japonica and P. involucrata , they will 
also be represented in the apex by a similar ring of desmogen- 
strands, which may be followed up as far as any differentiation 
can be distinguished in the meristem. Whether this apparent 
plerome extends past the youngest leaf, into the apical cone 
itself, is somewhat doubtful, but, on the whole, the probability 
is that it does so. 
Again, if in the differentiated regions of the stem the 
steles are irregularly scattered and widely separated, as in 
P. Auricula , the desmogen-strands which correspond to them 
are also found to be scattered in the merismatic regions of 
the apex ; and further, in this case it appears tolerably certain 
that no plerome is to be found in the apical cone itself. 
Therefore in these plants the study of the apical meristem 
throws no light upon the phylogenetic origin of the various 
types of structure ; such light can only be obtained from the 
ontogeny of the whole plant, as exhibited in the development 
of the seedling. 
The most striking feature in the apical region is the 
extreme insignificance of the development of the apical cone 
itself compared to that of the youngest leaf produced by it. 
The latter, immediately after its first formation, grows with 
great rapidity, completely overshadowing and pushing aside 
the minute apex which often becomes a mere lateral pro- 
tuberance at the base of the precocious leaf. Correlated with 
this early and excessive development of the young leaves, the 
leaf-traces also play a predominant part in the first appear- 
ance of the desmogen-strands in the meristem of the apical 
regions, especially in P. japonica and P. involucrata , where by 
z 
