1890.] Origin of the Plane-Trees. 803 
“A careful study of these expansions leaves no doubt of their 
strict homology with those so much more prominently shown in 
the extinct form, and the conclusion is at least natural that they 
are the surviving vestiges of a once prevalent organ. 
" Assuming the fossil form to be distinct from P. nobilis, which 
is, however, by no means certain, I have ventured to name it 
from the peculiar character above described, and to call it P. 
basilobata.” 
The close relationship of P. dasilobata to P. nobilis renders it 
obvious that the two must stand or fall together as representatives 
or ancestors of the genus Platanus. Moreover, it would seem 
that if they are to be excluded the whole series of ancient types 
to which they belong, must be removed from the ancestral 
line of descent of the surviving forms. It appears, therefore, to 
be essential to the argument that the quéstion whether they- 
belong to this line be settled at the outset. We will, therefore, 
consider Professor Jankó's objections to the platanoid nature of 
P. nobilis. These are, first, that “ It has five thick primary nerves 
(in a geological period in which this character is wanting in all), 
and from these very many (16-18) strong secondaries proceed 
parallel to one another without ending in teeth, their ends, how- 
ever, reaching the margin of the blade; moreover, these second- 
aries are well developed to the base of the primaries, which does 
not occur in the corresponding forms of Platanus.” In the 
second place, “The leaf is five-lobed at the beginning of a geo- 
logical period in which this form does not occur in the planes; 
moreover, the lobes are very well developed and large, the depth 
of the sinuses is of the third degree, although this depth does 
not appear until the end of the Miocene, and is not character- 
istic even in the Pliocene." Finally, he objects that * The margin 
of the leaf of P. zodilis is undulating and not toothed; whereas, 
in the planes in which the nervation is developed as it is in that 
Species, either teeth appear, or the margin is entire, in which lat- 
ter case the secondaries converge over one another." 
‘In reading these statements one naturally wonders from what 
Source Professor Jankó has derived his knowledge of this species. 
The chief objection seems to be that the leaves are five-lobed, 
Am. Nat.—September.—2, 
