238 BOTANICAL GAZETTE [SEPTEMBER 
under and the petioles allow drooping to occur. With the recurrence of thawing 
weather the blades expand and the leaf resumes its horizontal position. HANNIG™ 
has found that the rolling of the leaf is due to a loss of imbibition water by the 
cell walls, and especially by the walls of the spongy parenchyma. The move- 
ments may be artificially induced by conditions which cause the cell walls to lose 
water and so allow a contraction of the walls to occur. The formation of ice, 
excessive transpiration, etc. are such conditions. The author is inclined to regard 
this as the first known instance of hygroscopic movements by living leaves. To 
the reviewer it seems that he has made a closer analysis of the cause of the move- 
ments, and his discovery consists in showing that while turgor variation is 4 
prominent and accompanying feature, the real cause is the fluctuation in the 
content of imbibition water in the cell walls. It seems likely that many of the 
leaf movements which have hitherto been regarded as due to turgor changes may 
later be found to be caused by swelling and shrinkage of the cell walls. The 
author has not overlooked the fact that some leaves whose structure is apparently 
as well adapted to such movements as those of Rhododendron do not exhibit 
them.—Raymonp H. Ponp. 
Embryo sac of Nymphaea advena.—Miss SEATON’? has examined the em: 
bryo sac of this species, giving an account of its earlier stages. Abundant material 
has enabled her to fill in some desirable details. The archesporium is distinguish- 
able before the integuments begin to develop; and by division of the parietal cell 
and the epidermal cells the functioning megaspore becomes covered by 4 sterile 
nucellar cap six to ten cells deep. The sac develops a conspicuous tubular pro- 
longation into the chalaza, and the fusion nucleus rests in the narrow connection 
between this chalazal haustorium and the broader micropylar portion of the sac. 
At the first division of this nucleus there is no wall (contrary to previous observa- 
tion), and one of the daughter nuclei passes to the end of the chalazal tube. AS 
before reported for the family, the proembryo is spherical and almost completely 
invested by endosperm. The monocotyledonous character of Nymphaeaceae * 
inferred, but no new evidence for it is advanced. ‘This claim, which habitually 
accompanies the recent studies of Nymphaeaceae, is founded upon certain fi 
preconceptions as to what constitutes a monocotyledon. It might be wel i 
investigators of this group to try the effect of their work upon the rigidity a 
old definitions.—J. M. C. : 
Araucarians of the Atlantic coastal plain.—BeRRy™ has called ater 
anew to the wide distribution of araucarians in the Mesozoic, especially * eo 
trasted ‘with their present very restricted range. A Mesozoic distribution of 
12 HANNIG, E., Ueber hygroskopische Bewegungen lebender Blatter bei 
von Frost und Tauwetter. Ber. Deutsch. Bot. Gesells. 26a: 151-166. 1 gent 
*3 SEATON, SARA, The development of the embryo sac of Nymphaea 
Bull. Torr. Bot. Club 35: 283-289. pls. 18, 19. 1908. Jain. 
Berry, Epwarp W., Some araucarian remains from the Atlantic coastal P 
Bull. Torr. Bot. Club 35: 249-260. pls. II-16. 1908. 
