226 DUPLICATION OF GENERATIVE NUCLEI BY MEANS OF 
It will be a matter of theoretical interest to be able 
to control experimentally the production of chromoso- 
mal mutations. 
It might also prove to be of considerable economic 
importance to be able to produce at will the full range 
of chromosomal mutants in any plants, especially in 
those which are propagated by vegetative means. 
A. F. BLAKESLEE. 
I. INTRODUCTION 
Shortly I hope to be able to draw attention to the great significance 
of purposely obtained plurinuclear pollengrains” I wrote in February 
1921 (1921 b). 
This was written: 
1°. after it had been shown — in the spring of 1919 — that varieties of 
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Hyacinthus orientalis, submitted by the breeders to the influence of 
special external circumstances, formed pollengrains with a number 
of nuclei superior to the normal number. ; 
after exposure of the single-flowering variety Yellow Hammer 
which is characterised by the production of highly fertile pollen, 
under normal circumstances, — the percentage of sterile pollen- 
grains then always remaining below 10 — to such physiological sti- 
muli, as caused it to produce pollengrains with several nuclei, or 
such, which deviated, in a way presently to be discussed, from 
normal grains. 
In the same publication two other remarks, Eh may here be re- 
en were made: 
2. 
°. All investigated varieties — especially those with single fiona — 
possessed these abnormal pollengrains only, when they had not 
been cultivated under normal conditions. In all cases in which the 
conditions were normal the only difference observable between dif- 
ferent varieties, in respect to the pollen, was a greater or smaller 
degree of fertility. 
In reference to the production of the abnormal pollengrains men- 
tioned, it made no difference, whether the variety in question was : 
diploid or heteroploid, whether it had u or double flowers (cf. 
1921 b. p. 1134 and 1135). 
Such abnormal pollengrains were namely found in the case of 9 va- 
rieties with single flowers e.g.: : 
