Catamites and Dicotyledons . 143 
near a higher node. On the other hand, in some instances 
the foliar strands may pass to the higher node in the cortex, 
e. g. Menyanthes trifoliata , &c. It seems unnecessary to go 
further into this matter at the present time. It is worth 
while, however, to emphasize in this connexion that the only 
criterion of the node in plants with secondary growth is the 
point of exit of the leaf-traces from the primary wood. 
The interesting feature of these observations seems to be 
that parenchymatous organs, lenticular in shape and infra- 
nodal in position, occur in a number of Dicotyledons with 
secondary growth. Where the leaf-traces are verticillate 
and medullary diaphragms are present, these organs resemble 
most strikingly the infranodal organs of the Calamites. If 
a very large stem, possessing the structure of that of Potentilla 
palustris , were to have its parenchymatous parts macerated 
away and its medullary cavity filled with mud, the latter 
would produce a cast not unlike the very characteristic casts 
of Calamites. The only essential difference would be the 
fact that the constrictions in this case would really be infra- 
nodal, and not represent rings of tracheary tissue above the 
nodes, as in Calamites. 
The infranodal organs of certain palustrine Dicotyledons 
differ morphologically from those of the Calamites in the fact 
that they are the upper ends of foliar lacunae of the woody 
cylinder, whereas those of Calamites, as the writer has 
attempted to show, are the upper open ends of ramular 
lacunae. This is an important difference from the phylo- 
genetic standpoint, since it unites fhe Angiosperms with 
Filicinean ancestors, whilst for the Calamites a Lycopodi- 
neous ancestry is indicated. It is interesting that analogous 
structures should appear in groups genetically so remote, 
under similar conditions in life, and affords a striking example 
of the efficiency of homoplasy in originating similar structures. 
In conclusion, a few words should be said on the relation 
of branches and roots to the lenticular organs, although it 
is not necessary to go into this matter at length, since 
Dr. Scott will doubtless deal with it sufficiently in his 
