620 
Notes . 
ON THE GRAVITATION STIMULUS IN RELATION TO 
POSITION. — When an apogeotropic organ is placed on the inter- 
mittent klinostat 1 it is subjected to alternate stimuli tending to make 
it curve in opposite directions. If the organ is fixed say at an angle 
of 45 0 to the horizontal axis of rotation, the organ will, during half 
the time, point obliquely upwards, and during the other half it will 
point obliquely downwards. Are the gravitation stimuli equal in 
these two positions ? If so, no curvature will occur, but if Czapek 2 
is right in believing that 45 0 below the horizon gives a stronger 
stimulus than 45 0 above, it is clear that the organ must gradually 
curve towards the horizontal. 
Thirty-four experiments were made with grass-haulms (principally 
those of Lolium perenne ) fixed at angles varying between 35 0 and 55 0 
to the horizontal axis of the intermittent klinostat. In four cases no 
bending occurred, in twenty-seven cases the haulms bent from 2 0 
to 1 9 0 towards the horizontal, while in three instances they bent in the 
opposite direction or laterally. There can therefore be no doubt 
that grass-haulms obey Czapek’s Law in being more strongly stimulated 
at angles of about 45 0 below the horizontal than at corresponding 
angles when the free end points obliquely upwards 3 . 
The above observations were made some time ago in ignorance of 
the fact that Czapek 4 has used the same method in a cognate 
experiment. 
D. F. M. PERTZ. 
Physiological Laboratory, Cambridge, 
October , 1899. 
SOME OBSERVATIONS BEARING ON THE FUNCTION 
OF LATEX 5 .— The author has lately returned from a year’s sojourn 
in Ceylon, where he has been acting as scientific assistant to 
Mr. Willis, the Director of the Royal Botanic Gardens. During his 
1 For a description of the instrument see F. Darwin and D. F. M. Pertz in 
Annals of Botany, 1892, p. 245. 
2 Pringsheim’s Jahrbiicher, XXVII. 
3 The facts also agree, broadly speaking, with Elfving’s results, Acta Soc. Sci. 
Fennica, 1880. 
4 Sitzb. K. Akad. Wien, Bd. civ, 1895. 
5 Abstract of paper read before the Botanical Section of the British Association, 
Dover, Sept. 1899. 
