1907] CURRENT LITERATURE 229 
tuting the Bennettitales. The latter or some allied stock he regards as the pos- 
sible ancestors of the angiosperms, a probability which he considers strengthened 
by the incoming of the angiosperms as they became extinct.—E. C. Jerrrey. 
Stem-thickening in monocotyledons.—It has been claimed that in palms 
secondary thickening by means of a merismatic zone occurs, as in Dracaena. 
STRASBURGER’® has investigated the subject by a study of two stems of Wash- 
wngtonia filifera, and finds no cambial zone, but instead a number of localized 
areas in the pericycle where fundamental tissue, bundles, and sclerenchyma are 
produced. An examination of stems of Pandanus utilis afforded similar results. 
Among the numerous details recorded is the observation concerning the arrange- 
ment of the leaves in Pandanus; following SCHWENDENER the author finds that 
this is due to torsion of the stem axis. 
Another paper on Pandanaceae, by CARANO,?? denies the existence of second- 
growth in this family. Among other observations of interest is the crushing 
of vessels of the xylem at the leaf bases by growth of the wood parenchyma; 
this process seems to aid in casting off the old leaves. The bundles of the blade 
of the leaf show a horseshoe-shaped mass of phloem surrounding the xylem, and 
water-storage tissue is abundant along the median nerve. The root shows a 
number of large medullary bundles in addition to the peripheral ones, and to the 
former the lateral roots are attached. The roots springing from the stem are 
likewise connected with deeply situated vascular strands. These features hardly 
support the claim that this family is a primitive one. 
In the palm Euterpe oleracea3° the stem increases in thickness by the extraor- 
dinary growth of the mechanical tissue lying external to the phloem. This 
growth takes place after the stem has become hard and woody.—M. A. CHRYSLER. 
) Germination “ dimorphic fruits Snes has investigated the germinative 
Sorat to these differences in structure, he finds differences in germina- 
tive characters. The disk fruits germinate both in light and in darkness to a 
higher per cent. and more quickly than do the ray fruits. In the disk fruits 
diminution in the intensity of the light or its complete withdrawal only retards 
slightly the first stages in the germination, although it defers considerably the 
28 STRASBURGER, E., Ueber die Verdickungsweise der Stimme von Palmen und 
Schraubenbiumen. Jahrb. Wiss. Bot. 43:580-628. pls. 3-5. 1906. 
209 Carano E., Ricerche sulla morfologia delle Pandanacee. Annali di Botan. 
521-46. pls. oe 1906. 
3° KRANZL eber das Dickenwachstum der Palme Euterpe oleracea. Ber. 
Deutsch. Bot. Gini 24:483-489. 1906. 
Ernst, A., Das Keimen der dimogien Friichten von Synedrella nodijlora. 
Ber. Becta, Bot. Gesells. 24: 450-458. 1906. 
