272 
Fig. 11. 
Fig. 
Fig. 
Fig. 
Fig. 
wl. 
16. 
Fig. 18. 
EXPLANATION OF MIKROPHOTOGRAPHS 
A diploid pollengrain, again surrounded by sterile pollen. The alterna- 
ting dark and light spots in the vegetative nucleus indicate but slight 
condensation of the chromatine. x 480. 
A diploid pollengrain, lying between sterile and abnormal, plurinuclear 
grains. Next to the vegetative nucleus, the spindle-shaped generative 
cell; inside of the latter the compact generative nucleus, cut approxi- 
mately perpendicular to the longitudinal axis. The but slightly stained 
round spots are sections of starchgrains. Exine and intine plainly visible. 
020% d 
A diploid pollengrain with a vegetative and a generative nucleus, be- 
tween 2 diploid pollengrains, in which no generative nuclei have as yet 
been developed. x 480. 
Three pollengrains with diploid nuclei and four with haploid ones. The fo- 
cus is such that the size of the generative nucleus in the upper diploid 
pollengrain can be compared with that of the haploid nucleus in the pol- 
lengrains, below and above this one. x 480. 
At the top: an abnormal pollengrain with 2 globular haploid nuclei. At 
the base: a diploid pollengrain, the generative nucleus is in focus, al- 
most its entire length being visible. To the left at this pollengrain: an 
abnormal plurinuclear one, which has formed a bladderlike pollentube. 
Between these 3 pollengrains sterile ones of different sizes. x 480. 
Crosssection of the division zone of the root of a diploid seedling arisen 
from the cross Gertrude n. V. W.L. Q x Yellow Hammer abn. W. d. x 180. 
Crosssection of the division zone of theroot ofatriploid seedling from the 
same cross. Both sections are chosen in such a way that the relative size 
of the nuclei, of the cells and of the section as a whole are comparable. 
x 180. 
A number of cells of the under left quadrant of the section, pictured in 
fig. 17, x 1320. ‘In the center the nuclear plate, which can already be 
seen on the former photo; nearly all of the 24 chromosomes (12 long- 
ones, 6 of medium size and 6 short ones) are visible. 
re TT 
