1907] CURRENT LITERATURE 149 
of which leaves are the organs, and to consider it as a merely unavoidable evapo- 
ration whose amount depends upon physical factors that need to be exactly 
evaluated. What would be thought of an engineer who attempted to compare 
the performance of two boilers of different construction if he knew nothing of the 
heat units applied? Yet most of the so-called “‘comparative” studies of tran- 
spiration take no account of the fundamental energetics involved, assuming 
that when leaves are placed “‘under the same conditions” they have a like amount 
of energy for transpiration!—C. R. B 
Correlation and leaf size.—A. J. Ewart has published a short note dealing 
with correlation and leaf size.?8  LrypemMuTH has shown that adult leaves of 
Begonia and Iresine increase in size when allowed to root in the soil. EWART 
eee experiments on Tilia europaea, and found that adult leaves do not 
ncrease in size, even when most of the leaves are removed. However, a partial 
defoliation of young shoots causes a development of unusually large leaves, 
and the increase in size beyond the normal is due to an increase in the number 
of cells and not to an increase in their size, as supposed by LinpemutH. That 
increased size is due to an increased number of cells in such cases is not the 
common view.—H. C. Cowles. 
Presynapsis and synapsis.—Presynaptic and synaptic stages in the first 
division of the embryo sac mother cell of Adoxa are interpreted by LAGERBERG 
as follows.?9 Before synapsis the chromatin granules collect into groups which 
are often in pairs, apparently less numerous than the mature chromosomes. 
threads, so that at the beginning of synapsis there are two parallel threads which 
fuse as synapsis proceeds. The single thread which is thus formed is the thickest 
which appears at any time in this nucleus. Accordingly, the fusion of the male 
and female elements of the nucleus takes place during synapsis.— sJ 
CHAMBERLAIN. 
Embryology of Capsella.—The late Mrs. Mabel Schaffner’? left an incomplete 
paper on the embryology of Capsella, which her husband, Professor Joun H 
SCHAFFNER, has published. It is a detailed study of the development of the 
embryo of what is perhaps the most frequently used dicotyledon in teaching. 
Aside from the completeness of the series, the striking feature of the plates is 
that the whole series is drawn to the same scale, representing to the em = actual 
increase of the embryo in size at each stage of its development.—J. M 
a8 Ewart, A. J., ba influence of correlation upon the size of leaves. Annals 
of Botany 20:79-82. 190 
29 LAGERBERG, oe Ueber die prasynaptische — synaptische Entwicke- 
lung der Kerne in der ail Sma NE IY von Adaxa moschatellina. Botaniska 
Studier, tillagnade F. R. KJELLMAN. 8. 
SCHAFFNER, MABEL, The ate of the shepherd’s purse. Ohio Nat. 
AS pls. I-3. 1906. 
