THEIPS AS POLLINATOKS OF BEET FLOWEKS. 
To accomplish this a slit was made in one side of the bag at least 2 
inches below the buds of the inclosed spike, so that no pollen or thrips 
might fall upon the flowers when the vial was inverted over the slit, 
and the pollen-bearing thrips were jarred downward into the bag. 
This being done, the slit was closed with adhesive plaster, leaving 
the inclosed thrips free to seek the nectar and distribute the pollen 
they carried. About 25 
thrips were put in each bag. 
Three forms of control or 
checks were employed at 
this time: 
(1) Spikes of emasculated buds 
were isolated, as above described, 
and left undisturbed. 
(2) Similar spikes were isolated, 
and when the inclosed flowers had 
become receptive, slits were made 
in the bag and at once closed 
without introducing thrips. 
(3) Spikes of buds were pre- 
pared as for emasculation and iso- 
lated without that operation being 
performed. These also were then 
left undisturbed. 
One month later, all the 
bags were opened to exam- 
ine the inclosed flowers. 
The time had been too brief 
for the maturation of seed, 
but it was ample for fertil- 
ization and for the develop- 
ment of seed to the milky 
stage. The results were as 
follows : 
Fig. 5.— Spikes of beet flowers isolated by means of paper 
bags, showing the method of admitting pollen-bearing 
thrips through an opening. ( Original . ) 
Every flower on the checks remained sterile, the sepals of some remaining green. 
In other cases the entire flower had withered (PI. Ill, fig. 2). Among those to which 
thrips had been introduced, one set of flowers was lost; of a second set, 16.66 per cent 
of the flowers became fertilized and produced seed; a third showed 20 per cent of 
fertilization; and a fourth, 28.6 per cent. For the entire set, the percentage of effec- 
tive pollination by thrips was 20.37 (PL III, fig. 1). 
On August 26, 1911, eight spikes of wild-beet flowers were similarly 
treated. Three of these were used as checks. Thrips were placed 
with the others in the manner above described. Some of these spikes 
were afterwards broken off, but of those remaining none of the checks 
became fertilized ; of those to which thrips had been admitted only 
one remained, and 20.5 per cent of its flowers had been fertilized and 
produced seed. 
