1921] CURRENT LITERATURE 53 
or the south Pacific than to America. The American elements that are 
. present are accounted for partly through introduction by winds or migratory 
birds, and partly as a residue of once more widespread forms that are now 
extinct except in Hawaii and America. The absence of conifers may similarly 
be explained by extinction, if they were ever present, or by the absence of 
suitable soil conditions. The almost complete absence, for example, of granitic 
or calcareous soils might well explain certain absences. It is noted also that 
great ocean deeps separate Hawaii from America, whereas it is much shallower 
between Hawaii and the Orient. It is concluded, therefore, that the Hawaiian 
flora has been derived for the most part from the southern Pacific region, and 
that the Hawaiian Islands are a remnant of a northeastern extension of some 
large land mass, once connected closely with south Pacific lands.—H. C. 
COWLES. 
Studies of cambium.—BaILeEy,™ in a third paper on cambium, has 
made what he calls a cytological ‘‘reconnaissance.’’ In the preceding paper, 
reviewed in this journal,*5 he called attention to the size variations of cambial 
initials, and to the unusual opportunity offered by the cambium for the study 
of a number of fundamental cytological problems. In this preliminary study 
he has reached the following conclusions. The initials of the cambium, which 
may attain a length of more than gooo pw, are uninucleate, and the “working 
ousand microns. The nucleo-cytoplasmic ratio may be relatively constant 
in ray initials, but varies enormously in fusiform initials. All the cambium: 
initials of Pinus Strobus contain the diploid number of chromosomes. Small 
ray initials may contain as large chromosomes as adjacent fusiform initials 
with a volume 200-1000 times as large. Fusiform initials, which are frequently 
several hundred times as long as they are wide, divide longitudinally by an 
extraordinary extension of the cell plate. The various types of cell plate 
formation described by various cytologists are believed to be merely different 
Phases or stages of a single general type of cytokinesis. These glimpses 
would seem to justify the writer in his belief that the cambium well deserves 
intensive cytological investigation.—J. M. C. 
Economic plants of Philippines.—In an illustrated report Brown” gives 
a series of descriptions of the indigenous food-producing plants of the Philip- 
pines. Many will be surprised to find the statement that the edible wild 
Plants of these islands are less abundant, more inaccessible, and inferior in 
AtLEy, I. W., The cambium and its derivative tissues. IIT. A reconnais~ 
sance of cytological phenomena in the cambium. Amer. Jour. Bot. 7:417-434. 
bls. 26-29. 1920. 
*§ Bot. Gaz. 71:408. 1921. 
‘6 Brown, Wa. H., Wild food plants of the Philippines. Phil. Dept. Agric. and 
Nat. Res., it For. Bull, 21:1-165. figs. 81. 1920. 
