JuxLy 16, 1897.] 
group, which was compared with another fossil 
species, P. appendiculata of Lesquereux, in 
which somewhat similar basilar expansions oc- 
eur, but in this case separate from the main 
blade. The latter species comes from the Au- 
riferous gravels of California, a much later for- 
mation, and it was argued that these two cases 
indicate a gradual separation of these lobes 
from the blade as having taken place in the 
progress of development. It was further shown 
that the living American species, P. occidentalis, 
sometimes has a small expansion at the base, 
through which the petiole passes, and that 
other cases may be found on young shoots in 
which these lobes are distinct from the blade. 
The second paper cited, though chiefly a 
criticism of a memoir by Janké6, on the leaves 
of Platanus, discusses the subject of basilar ex- 
pansions with additional illustrations. 
Dr. Hollick’s papers deal with an almost 
similar condition of things in the fossil species 
of Liriodendron. Both of these genera belong 
to what are known as waning types, and their 
present foliage has reached its highest state of 
development, 
These and other facts that have been from 
time to time coming to light had begun to im- 
bue botanists who had given attention to the 
subject with the general idea that stipules are 
morphologically portions of the leaf that have 
been gradually separated from the existing leaf 
blade through a process of development going 
on under the influence of the great principle of 
advantage in biology, which relegates to the 
domain of vestiges or obsolescent organs every- 
thing that has ceased to benefit the organism, a 
process which has as its ultimate result the 
complete extinction of such organs, and there 
is no doubt that in many cases modern exstip- 
ulate leaves have once had stipules and lost 
them, although it is also true, as Mr. Tyler 
shows, that in other cases, especially those of 
sessile leaves, no stipules have ever existed. 
In 1894 Mr. Morong, in treating the genus 
Smilax,* said: ‘‘ Most of the species climb upon 
other shrubs and trees by means of a pair of 
tendrils which grow at the summit of a stipular 
wing on each side of the petiole, often not de- 
* Bull. Torr. Bot. Club, Vol. XXI., No. 9, Septem- 
ber 29, 1894, p. 420. 
SCIENCE. 
101 
veloping till the stem is several years of age;’’ to 
which he adds in a footnote: ‘‘De Candolle 
regards this appendage as more in the nature 
of a modified leaf segment or leaflet than a 
stipule, but it seems to me that a stipule is noth- 
ing else than a leaflet at the base of a petiole.”’ 
Mr. Tyler does not note this statement of Mr. 
Morong in his bibliographic summary, but it is 
characteristic both of Mr. Morong’s keen insight 
into such matters and also of the general drift 
of botanical thought on the subject. 
In the paper before us there are brought out 
into clear light at least three distinct and highly 
important facts. The first relates to method. 
It had long been felt that the great need in 
botany was the study of plants from the em- 
bryological standpoint in some such way as 
animals have been studied with such remark- 
able results. The two great sources of our 
knowledge of development in both kingdoms 
are, first, paleontology, and second, embryology. 
Both of these had been almost totally neglected 
by botanists until within recent years. Some- 
thing, it is true, had been done along the more 
general lines of plant development from the 
paleontological side, but scarcely anything 
in connection with the transformation that 
leaves undergo, and the few papers above 
quoted constitute practically all that has been 
done in this line. A number of attempts have, 
however, been made to approach the vege- 
table kingdom from the embryological point of 
view. But the seed being regarded in a certain 
sense as the homologue of the egg, most of 
these attempts have been devoted to the study 
of the seed and of seedlings, the great work of 
Sir John Lubbock constituting the most ex- 
haustive of these efforts. 
Mr. Tyler has shown in the present paper 
that the study of plant embryology should not 
proceed from a consideration of seeds and their 
development, but of buds, and that while 
botanists have been mainly seeking for light in 
the difficult study of seed embryos, the true 
source of such knowledge is the much more 
accessible phenomena of bud development. 
The figures that he has given abundantly de- 
monstrate this truth, and henceforth there can 
be no doubt that botanists generally will pro- 
ceed according to this method and that the 
