1922] SEARS—TARAXACUM 435 
section. Leaf area being given in terms of square millimeters 
and capacity figured in terms of fourth powers of micromillimeters 
the latter have been multiplied by 10~"? to get both sets in terms of 
a common unit. For the sake of compactness these figures are 
multiplied by 10° before tabulation, as noted in tables. The 
foregoing data will be found listed in tables I-VA and plotted 
in figs. 5 and 6. Here are also included counts of the number of 
vein islets per unit area of leaf, taken at mid-distance between 
margin and midrib and averaged from several counts in each case. 
TABLE I 
DIAMETER FREQUENCIES OF XYLEM TUBES FOR SUCCESSIVE LEAVES OF SEEDLING 
PLANT SA; EACH UNIT REPRESENTS 3.34 
Diameters 
Leaf no ; 
ba ris 2.0 2.5 3.0 | 3.3 4.0 
Rae iee a ee I 2 3 7 ir _ 
Pie is eiage 3 9 12 9 ‘ 2 2 
Sie ae 15 6 6 3 2 
Rika e a 3 bane 2 4 12 5 3 5 7 
BN rid ewe ela 3 4 16 7 5 
| 
TABLE IA 
OTHER DATA FOR SUCCESSIVE LEAVES OF SEEDLING PLANT SA 
Leaf nos, 
I 2 3 4 5 
Leaf a 250 12 I 
Total . rohit capacity Pies ee ¥. 57 L/S$2 0.32 2.47 °.73 
Mean xylem capacity X108...... 0.0510 0.0346 0.010% 0.0652 0.0222 
Total capacity  ro8 
tale 0,006 ©,0025 0.0165 ©,0073 
TABLE II 
DIAMETER desercapess OF XYLEM TUBES FOR SUCCESSIVE LEAVES OF SEEDLING 
ANT SB; EACH UNIT REPRESENTS 3.3 ¢ 
Diameters 
Leaf no. SeGRERUT CHERIEN near MERELY ET ee EMIS : 
1.0/1.5] 2.0] 2.5 | 3.0/3.5 |4.0|4-5|5.0/5.5|6.0/6.5|7.0|7.5 | 8.0 | 8.5 
Pe ra 3 9 Pete 8 ey ee) 4 6 I 
As I 6 & 4 16° to 9 8 1 4% 5 2 I 
3... I Bi te) 32 a) It 4 7 2 3 2 
Wes crea ae I S458 | 25 | 34 535 o 1) EY 38 I I 
RS ear eegedliv cr matics 2 6 -t to |3a 65 7 26 32 2 
Oc ta ee 3:1 40 7 ols 12 7 2 
Z-+++. S16) 8 bis 10 7 Itt 44 et 
eee 6 5 1s Ir 2 
