PHYSIOLOGICAL STIMULI AND ITS SIGNIFICANCE 245 
ploid or the triploid nature of a nucleus, a fact, about which I hope soon 
to give further information. 
A perusal of the table on the next page, giving a résumé of all crosses 
and self fertilisations, of the number of flowers treated, the number of 

Fig. 3. 
Camera lucida drawing of the nucleus of mikrophoto n°. 18. Explanation see 
there. The numbers 1—12 indicate the long chromosomes, 13—18 those of me- 
dium size and 19—24 the short ones. x 2240 approximately. 
seeds obtained, of those sprouted etc. will teach us 1°. that hyacinth- 
varieties are selfsterile to a considerable degree and 2°. that by no 
means all apparently good seeds sprout. Seeds which did not sprout in 
1922 and were left in the pots until 1923 did not sprout either. 
It was thought advisable to publish this result now and not to post- 
pone publication until the other roots had all been investigated, as I 
dispose of too little leasure, to be able to complete the investigation 
within a reasonably short time, the less to, because the pollination-ex- 
periments have been continued in 1922 and 1923. 
At the present time, heteroploid varieties of Hyacinthus orientalis 
(Cf. 19205, especially) are chiefly cultivated, so that it seems to me de- 
sirable to point out that every precaution has been taken to prevent, 
that the diploid varieties, used in the experiment, should be pollinated 
by pollen of heteroploid varieties, which could cause the forming of a 
heteroploid seedling. 
