Botany. — “On the influence of circumstances of culture on the 
habitus and partial sterility of the pollengrains of Hyacinthus 
orientalis”. By Dr. W. E. pr Mor. (Communicated by Prof. 
A. H. Braauw.) 
(Communicated at the meeting of February 26, 1921). 
I. Introduction. 
When, in the spring of 1919, it had become evident to me 
that the nuclei of the single-flowered, rose-coloured hyacinth-variety 
Nimrod possessed 19 chromosomes’), I thought it advisable to examine 
the fertility of the pollen and to compare it with that of the Dutch 
varieties with 24 chromosomes in the somatic cells, which number 
IT at that time still considered as diploid. I chose for that purpose 
the closed anthers, taken from growing Nimrod-plants that belonged 
to the same grower as those of which I had fixed the root-tops in 
behalf of my chromosome-examination. To my surprise the pollen- 
grains in these anthers differed greatly from the aspect which hya- 
cinth-pollen had always shown to me. I did not find one normal 
fertile grain. The sterile pollengrains were elliptic, round or tri- 
angular in shape and had various dimensions. The wartlike protu- 
berances on the exine, which in normal cases cause the pollengrains, 
when plunged into a drop of some liquid, to stick together to some 
extent, were undeveloped, so that the pollen dispersed very easily. 
Apart from these sterile pollengrains, there appeared in the prepa- 
rations many that were much larger and globe-shaped, and were 
full of large starchgrains. If the pollen was put into a diluted 
solution of jodine in jodide of potassium, one saw at once the 
abnormal pollengrains lying like intensely blue-black globes among 
the yellow, shrivelled exines of the sterile pollengrains. In a drop 
of water the exine usually burst rather soon and the starchgrains 
1) Over het optreden van heteroploide Hollandsche varieteiten van Hyacinthus 
orientalis L. en de chromosomengarnituur van deze plantensoort. 
Verslagen van de Koninklijke Akademie van Wetenschappen te Amsterdam, Wis- 
en Natuurkundige Afdeeling, Deel XXIX, p. 518. 
Nieuwe banen voor het winnen van waardevolle varieteiten van bolgewassen, 
p. 1% 
83 
Proceedings Royal Acad. Amsterdam. Vol XXIII. 
