EXPLANATION OF MIKROPHOTOGRAPHS 
The figures are found on Pl. I—VI as follows: Pl. I fig. 1 and 16; 
Parse 2rand}17; Pl.IIFfig,3=6; Pl. IV fig. 7,8, 9, 11andıl2; 
Pl. V fig. 10 and 14; Pl. VI fig. 13, 15 and 18. 
Fig. 1—5 refer to pollen of Hyacinthus orientalis Yellow Hammer abn. W., which 
served to fertilise the variety Gertrude. 
Fig. 1. Longitudinal section of an anther, showing the content of both loculi of 
one theca. The black globes are diploid pollengrains. In their proximity 
some plurinuclear pollengrains. The rest consists, with the exception of 
few normal, fertile pollen grains, of aborted ones. X 66.5. 
Fig. 2. The upper part of the same theca. x 182.5. 
Fig. 3. A sprouting abnormal pollengrain with 2 haploid nuclei. Nucleolus and 
the clear area around it, plainly visible. The exine is visible at the right. 
| To the right of this sprouting pollengrain: sterile grains. At the left a 
sterile pollengrain is seen adpressed to the distended pollentube. x 576. 
Fig. 4. A sprouting abnormal pollengrain with 3 haploid nuclei. In the disten- 
ded pollentube one nucleus, the largest one, is in front; this is the vege- 
tative nucleus. x 480. 
Fig. 5. A sprouting abnormal pollengrain with at least 5 haploid nuclei. The 
exine (at the left) and the bladder-like pollentube (at the right) are in 
focus. Inside of the exine 2 globular nuclei are seen. Of the nuclei, pre- 
sent in the pollentube, 2 can vaguely be seen. Below this pollengrain : 
an abnormal grain, in which one nucleus is seen near the end of the dis- 
tended pollentube. In its proximity sterile pollengrains. x 480. 
Fig. 6. A sprouting abnormal pollengrain with 4 globular, haploid nuclei. x 480. 
Fig. 7. An abnormal pollengrain with 5 crowded haploid nuclei, the one in the 
center of the group indistinct, while out of focus. x 480. 
Fig. 8. Between two diploid pollengrains an abnormal one showing karyokine- 
sis. On focussing at different levels 8 chromosomes are seen, SO that the 
grain is haploid. Of the 8 chromosomes 4 are long, 2 of medium size and 
2 short. At the upper side of the mikrophoto an abnormal plurinuclear 
pollengrain in which one of the globular nuclei begins to divide. x 480. 
Fig. 9. A diploid pollengrain in which the vegetative nucleus and a generative 
one are quite distinct. x 480. 
Fig. 10. A diploid pollengrain with a vegetative nucleus and 2 generative ones. 
It is surrounded by sterile pollen. Both in this case and in the former one, 
the knife has cut away part of the generative nuclei. x 480. 
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