" 1896] CURRENT LITERATURE 505 
this point may be obtained when the early stages in the endosperm formation 
of gymnosperms has been more thoroughly worked out. It is to be regretted 
that Dr. Arnoldi did not extend his work into the embryogeny of the sporo- 
phyte. Additional evidence upon the suspensor formation in this group may 
help to answer the question concerning the supposed relationship of lyco- 
pods and gymnosperms.—O. W.C 
Mr. J. H. HArtT discusses briefly" the so-called ‘irritability’ of the 
flowers of Catasetum tridentatum Hook., of which Darwin gives an account 
in his Fertilization of Orchids. In opposition to Darwin’s observations he 
says : 
_ “The ejection of the pollinia can be caused by other means than the 
irritation of the antennz by touch . . . . A concussion of the flower, 
the removal of the anther cap, and pressure exerted on almost any part of 
the column, and especially any irritation on the margins of the stigmatic pit 
ag a this readily if the flower is at a favorable stage of maturity. 
: the expulsion of the pollen does not depend upon any 
Special viability, but upon mechanical action alone.” 
“The antennz are seen to be merely a prolongation of . . . . the 
_ edges of the stigmatic pit . . . . Apart of thiscurl . . . . holds 
the margin of the caudicle . . . . The antennae at. . . . anthesis become 
turgid, stiff, and non-elastic. In this state they furnish levers which are 
amply ent e cause a disturbance of the grip they hold upon the margin 
of the caudicle. 
The question needs further study. It is one which can only be satis- 
peorly examined in a tropical laboratory.—C. R. B 
A BRIEF suMMARY of MacDougal’s work on the mechanism of curvature 
o tendrils is as follows: Those tendrils which are irritable to contact are 
of such great difference in morphological derivation, anatomy, and degree of 
‘intitability, that it is unsafe to assume their mechanism to be identical. The 
“urvature of a tendril about a support as a direct reaction to irritation, and 
me coiling of a free portion, are entirely distinct and largely independent 
Processes, 
_ Curvature in the tendrils of Passiflorea: is due to the contraction of the 
tissues of the concave side, which theory is not in harmony with that of 
De Vries, viz., that increased osmotic activity of the convex side results in an 
different, that of the concave side being more richly granular, and more 
rly filling the cell cavity. The density of the protoplasm of the concave 
ee 
‘aay Misc. Inform. Roy. Bot. Gard. of Trinidad 2:225. 1896. 
Annals of Botany 10: 373-402. 1896. 
