74 BOTANICAL GAZETTE [JANUARY 
so arranged that the rotating plant describes a cone whose axis is inclined to the 
horizontal leads him to announce the following statements. The optimum 
position for geo-perception is horizontal and equal responses are induced by 
equal deviations above and below the horizontal. (In a recent paper NEw- 
cCoMBE”® finds that roots and stems do not receive equal stimuli at equal angles 
above and below the horizontal.) The minimum perception time is extremely 
brief, less than two-thirds of a second. A proportionality between reaction time 
and perception time does not exist. Orthotropic organs can be geotropically 
stimulated even though the rotation be very rapid and uniform. There is a 
threshold-difference not only for intensity of stimulation but also for duration of 
stimulation, and for position during stimulation (deviation from horizontal). 
Intermittent is much less effective than continuous stimulation in the induction 
of geotropic curvatures. The response is little affected by the duration and num- | 
ber of individual stimulations. The presentation time is never smaller than for 
continuous stimulation, and is practically the same as for the latter when the 
ratio of stimulus duration to rest duration is as small as 1:5. The duration of 
single stimuli is without influence upon reaction time so long as the ratio of rest — 
duration to stimulus duration does not exceed 5:1. Nothing was observed which © 
would support HABERLANDT’S statolith i on H. Ponp 
SPINDLE FORMATION in the pollen mother-cells of Cassia tomentosa L. has 
been studied by Hus,'? who finds that the cytoplasm of the young pollen mother- 
cell consists of a network of fibers more or less radially arranged, on and between 
which large and small granules are found. The meshes adjacent to the nuclear 
wall become smaller and elongated parallel to that wall. A granular zone appears 
around the nucleus; and at the same time there appears in the cytoplasm deeply 
staining rough fibers frequently arranged in conical groups. A felt-like zone, 
partially or sometimes completely surrounding the nucleus, next appears, and the 
deeply staining rough fibers of the cytoplasm, now united into cones, establish — 
connection with the fibers of the felt-like zone. The linin threads become parallel 
with the other fibers and also parallel with the axis of the larger or ascendant cone. 
As soon as the rough tents of the nies become RTH ~ nucleolar —_ 
breaks down, the linin and th ] 
into bundles. A multipolar spindle % is formed, two cones of which, opposite to 
each other, are more prominent and gradually absorb the smaller cones. The 
narily met with in dividing mother-cells of pollen, spore, and embryo-sac, and the 
multipolar diarchal spindle Anlage described for vegetative cells.’—W. J. G 
LAND. 
16 NEWCOMBE, F. €., Limitations of the klinostat as an instrument for scientific 
research nce 20:376-379. E904. 
‘7 Hus, Henrr T. A., Spindle formation in the pollen mother-cells of Cassia — 
tomentosa L. Proc. Calif. Acad. Sci. III. 2: 329-354. pls. 30-32. 1904. 
