16 
son the work will be of special interest to the 
plant physiologist. The abstracts used in the 
preparation of the several monographs have 
been accurately prepared and the numerous ci- 
tations to the original literature enhance the 
value of the work very much. If in courses 
of plant physiology it were required of the 
student to isolate all of these plant products 
it would add very much to the student’s com- 
petence to deal with the nature of physiolog- 
ical processes and make this subject of greater 
fundamental value in its application to other 
phases of botanical work. 
The second edition has been improved by 
re-writing the section dealing with the chem- 
istry of plant pigments. This subject during 
the past few years has been the field of most 
interesting study by Willstitter and Miss 
Wheldale. 
The value of the work would be much en- 
hanced by a somewhat different arrangement 
of the subjects, particularly if they could be 
connected in their biological relations. To 
begin with “fats, oils and waxes,” substances 
which are seldom studied in courses in either 
plant morphology or plant physiology, tend to 
discourage the use of the book by those for 
whom it would be a source of greatest benefit. 
On the other hand if a subject like the car- 
bohydrates or pigments were first considered, 
both of which are under constant observation 
by the student of botany, it is quite likely that 
the chemical methods contained in the work 
would be applied in laboratory instructions. 
Furthermore the microchemistry of all of the 
plant products considered should be consider- 
ably improved upon. Many of the statements 
are only partly true; in others more pro- 
nounced reactions could be utilized while in 
still others a large amount of work should be 
included. To-day the interest in microchemis- 
try or chemical microscopy is very great and 
with the appearance of such excellent works 
as those of Chamot, Molisch and Tunnmann 
there is an excellent basis in a work of this 
kind to connect the morphology of plants with 
the chemistry of the constituent and to follow 
physiological processes with microchemical re- 
actions.: Henry Kraemer 
June 1, 1918 
SCIENCE 
[N. S. Vou. XLVIII. No. 1227 
SCALARIFORM PITTING A PRIMITIVE 
FEATURE IN ANGIOSPERMOUS 
SECONDARY WOOD 
Proressork JEFFREY, in his recent stimula- 
ting book, “ The Anatomy of Woody Plants,” 
Ch. VII., derives the vessel with the simple or 
porous type of perforation from the fusion otf 
horizontal rows of circular pits in the end- 
wall, the scalariform pit and perforation be- 
ing merely an intermediate stage in the proc- 
ess. Perhaps such a reversible evolution has 
gone on in certain groups, although it is here 
attempted to show that the available evidence 
is capable of the opposite interpretation. 
Multiperforate and even uniperforate end- 
walls in gymnospermous vessels may arise from 
the fusion of circular pits with the dissolution 
of the closing membrane as Professor Jeffrey 
describes for Hphedra; but this fact seems 
inadequate to explain either the presence of 
sealariform pitting or the wide prevalence of 
sealariform perforations in the vascular ele- 
ments of the less specialized angiosperms. It 
does not appear that all of the facts germane 
to the subject have been fully considered. In 
tracing out the development of vascular ele- 
ments with uniperforated end-walls in accord- 
ance with Jeffrey’s hypothesis, serious difi- 
culty is met. 
The scalariform pits in conservative regions 
of the secondary wood of Liriodendron, Drimys, 
Asimina, and other forms with prevailing 
circular pits in the less conservative regions, 
suggest antecedence of the scalariform con- 
dition, while a further illustration is afforded 
by the monocotyledonous Dracena. Thus, in 
Dracena aurea, typical secondary xylem with- 
out vessels is formed, the fibro-tracheids of 
which have cireular pits in their lateral walls, 
but typical scalariform pits in the walls of the 
overlapping tracheid ends. There is no in- 
dication that such sealariform pits have arisen 
from the fusion of rows of circular pits. 
They are evidently a primitive feature of the 
tracheid and closely resemble the scalariform 
pits of the secondary wood tracheids of 
Drimys found in the vicinity of the pith; 
yet only a slight modification of the tracheids, 
with dissolution of the closing membranes and 
borders of the scalariform pits, would com- 
