198 
GENETICS: J. BELLING 
Proc. N. A. S. 
that the three are homologous. 2 Hence we may define a triploid plant, 
in the strict sense, as one having a chromosome group made up of a number 
of sets of three homologous chromosomes. 
In diploid plants there is an attraction of some kind between the two 
homologous chromosomes which form a bivalent or dyad at the first 
division. We may expect an attraction also between the three homolo- 
gous chromosomes in the corresponding triploid plants, leading to the 
FIG 1 
The drawings were made at stage height, with the Abbe camera. A I,eitz 2 mm. apo- 
chromatic objective of 1.3 aperture, and compensating ocular 6 were used. An achro- 
matic condenser of 0.9 aperture was focussed on the object so as to give critical illum- 
ination. The pollen-mother-cells were fixed and stained with iron-aceto-carmine (1). 
The assortment of the chromosomes in the pollen-mother-cells of a diploid 
Canna clone. This was obtained under the name "Madame Crozy." (1) Prophase 
of the first division, showing 9 bivalents. (2) Metaphase of the first division, showing 9 
dyads, one already divided. (3), (4), (5), (6), and (7) are stages of early anaphase, 
showing division of the 9 dyads into 9 + 9 chromosomes. (The arrows indicate the 
situation of the polar axis.) (8) After the first division, showing 18 chromosomes. 
(9) The two groups in the metaphase of second division, separated by a cell-wall. 
