COMMERCIAL DUTCH-BULB CULTURE. 
21 
The sizes of bulbs as employed in the descriptions of commercial 
varieties are likely to be confusing to an American, for two reasons : 
(1) The metric system is used, and (2) the listings are for bulb cir- 
cumference instead of diameters, as practiced with freesias in Cali- 
fornia. Since all business is done on this basis the prospective bulb 
grower must accustom himself to these terms. Indeed, the matter is 
not really complicated. The sizes of foreign-grown bulbs are always 
given in centimeters, abbreviated to " cm." To translate the centi- 
meter into inches one needs only to divide by 2J. This gives the cir- 
cumference in inches. If one wishes to arrive at the diameter, a fur- 
ther division by 3 will give the approximate result. For instance, a 15 
cm. bulb will have a circumference of 6 and a diameter of 2 inches. 
The sizes of bulbs as used in commercial culture vary with each 
grower, and even may vary from year to year with the same grower, 
depending upon the land available, the fertility of soil, and other 
factors. In short, his 
grades are matters of 
size, and size is a mat- 
ter largely of conveni- 
ence and varies with 
fertility, age, variety, 
etc. 
In the work of the 
Department of Agri- 
culture approximate 
sizes have been adopt- 
ed. These relate en- 
tirely to the growing end of the business and do not enter into com- 
merce. The sizing thus far has been done mainly by the conventional 
circular nesting sieves of the Netherlands. These have parchment 
screens and are operated by being shaken in the hand or, when nested, 
in a hand shaker, several sizes then being sorted at once. This method 
works well for small quantities of bulbs. For large quantities other 
forms of machines are in use. One recently constructed is a revolving 
drum of parchment, its operation being not essentially different from 
a gravel screen. The most commonly used machine, however, consists 
of an oscillating plane made up of a series of sieves placed end 
to end with suitable chutes on either side to receive the different 
sizes. (Fig. 12.) 
This matter of sizing machinery will require the attention of im- 
plement manufacturers, and there is little doubt that the heed will 
be met as the occasion demands. The essentials are separating 
sieves, an operation that will not bruise the bulbs, and a good blower. 
The parchment screens are made with perforations 3 to 24 centi- 
meters in circumference. In the sizing of tulips we have employed 
Fig. 12. — A bulb sizer used extensively in the Netherlands. 
