Vol. 7, 1921 
BOTANY: HARRIS AND SINNOTT 
37 
and trimerous seedlings is conspicuously shown by the frequency distri- 
butions of two of the lines shown in diagram 1. 
In passing upward from the base of the hypocotyl, each primary bundle 
pair normally divides into two so that in the central region of the hypocotyl 
the bundle number is normally twice the number of primary double bundles 
at the base, plus the intercalary bundles. In many cases the number is 
somewhat in excess of this, however, showing either that new (intercalary) 
bundles have appeared or that some of the bundles have become sub- 
divided. 
The modal number of bundles in the mid-region of the hypocotyl is 
eight or ten in dimerous plantlets ; in trimerous and hemitrimerous plantlets 
30 
• *=U/MEROUS 
80 
o o=T TV ME ROUS 
70 
eo 
so 
I / 
40 
30 
20 
JO 
Q 
L Lt/VF 98 
| \ LINE 143 
8 9 10 II 
12 13 14 15 16 17 
8 9 10 II 12 13 14 is ie n 
DIAGRAM 1 
Percentage frequency distributions of total bundles (primary double bundles counted 
as two) at the base of the hypocotyl in dimerous and trimerous seedlings 
of two lines. Abscissae represent bundle numbers, ordinates 
represent percentage frequencies. 
it is twelve. On the average the number is from 1.7 to 3.8 bundles higher 
(or from 15.7 to 47.9% higher) in the trimerous than in the dimerous 
seedlings. The differentiation of the two classes of seedlings in their 
vascular anatomy at the level is clearly shown in diagram 2. 
The bundles in the mid-region of the epicotyl show in dimerous plantlets 
a modal number of twelve, whereas in trimerous seedlings it is fifteen. 
On the average there are from 2.8 to 3.7, or from 23.0 to 30.2%, more 
bundles in the epicotyl of the trimerous than in the dimerous seedling. 
