176 
the other. In 1869 Williamson was able 
to point to similar structural modifications 
in Dadozylon, and to show that regularly 
transitional forms gave proof of the deriva- 
tion of the bordered pits from scalariform 
structure. Recent studies of North Ameri- 
can Cordaitz have given conspicuous ex- 
amples of the same kind, and show that a 
continuous series of radial sections will 
display regularly transitional forms—often 
combined in the same tracheid—passing 
from the spiral vessels of the protoxylem 
through scalariform vessels, thence into 
tracheids with transversely elongated bor- 
dered pits, which successively become short- 
ened up until there is developed the typ- 
ical, multiseriate, hexagonal and compactly 
crowded bordered pit so well defined not 
only in the Cordaitze, but also in the mod- 
ern Araucariese. These facts possess the 
deepest significance from a phylogenetic 
point of view, since they afford an addi- 
tional and reliable indication of derivation, 
and in the present connection, they serve to 
point with considerable force to the idea 
that among modern Conifera, the widely- 
separated bordered pit which in many in- 
stances wholly disappears is for that line 
of descent the culminating form of this type 
of structure; while in the Angiosperms 
the modification has been carried to a 
greater extreme and involves the reduction 
of the pit to the form of a simple slit or 
pore, and ultimately to its complete oblit- 
eration as a final expression of the second- 
ary growth of the cell wall. Structural 
alterations of this nature involve also a 
more or less profound influence upon func- 
tional activity as expressed in the distribu- 
tion of nutrient material. 
I have thus endeavored, within the limits 
of the time at my disposal, to briefly indi- 
cate some of the more prominent directions 
in which paleobotanical activities have de- 
veloped in North America within the last 
decade. While this review shows that some 
SCIENCE. 
[N. S. Vou. XIII. No. 318. 
substantial progress has been made, that 
much has been accomplished in the direc- 
tion of laying the foundation for future 
studies, and that the study of fossil plants 
is gaining greater prominence as a necessary 
aid to our knowledge of plant descent, it 
also brings into relief the fact that progress 
in this latter direction must of necessity be 
slow, and the result of laborious methods of 
investigation extending over such long pe- 
riods of time as will permit the accumula- 
tion of great stores of material, and the 
careful piecing together of fragments which 
separately have little or no significance. 
Nevertheless the rapid progress which has 
marked our knowledge of fossil plants dur- 
ing the last twenty years, and the acceler- 
ation of this progress within the last two 
decades, together with a greater apprecia- 
tion of the fundamental importance of such 
studies in questions of relationship, afford 
much ground for regarding the future of 
paleobotany on this side of the Atlantic as 
one of promise. 
D. P. PENHALLOW. 
McGILL UNIVERSITY. 
DETERMINATION OF THE SUN'S DISTANCE 
FROM OBSERVATIONS OF EROS. 
Tue tendencyof the time toward thorough 
_organization and cooperation in large en- 
terprises is well illustrated in modern as- 
tronomy. Twenty-five years ago, a dozen 
leading observatories, by mutual agreement, 
divided the northern sky into zones in such 
a way that their meridian circle observations 
would combine to form the excellent Astro- 
nomische Gesellschaft star catalogues ; and 
this great work is now nearing completion. 
The work of charting the sky by means of 
photography was similarly organized by the 
Astrographic Conference in Paris some ten 
years ago. 
About fifty of the principal observatories 
of the world are now cooperating in a great 
program of observation for improving our 
