EFFECTS OF CKOSS-POLLINATION ON SIZE OF SEED IN MAIZE. 



11 



from the same plant that was behig pollmated, iii which case the result- 

 ing white seeds were not only pure for the variety, but were self- 

 poUmated. The two kinds of seeds were, of course, mixed indiscrimi- 

 nately on the ear and developed under identical conditions. Where 

 consistent differences in the size of the two kinds of seed occur it is 

 therefore safe to assume that they are due to differences mduced by 

 the use of the various kinds of pollen. The number of seeds from 

 a single ear are usually large enough to afford reliable averages and 

 justify confidence in even relatively small differences. 



Eleven such ears were secured, and the results with respect to the 

 weight of the hybrid and pure seed are given in Table I. Individual 

 plant numbers are given, since in many instances a plant which bears 

 one of the pollmated ears also figures as the source of pollen m another 

 cross. Where more than one ear of a plant was pollinated the second 

 and third ears from the top of the plant are given the individual plant 

 number followed by a figure 2 or 3. To avoid large decimals, the aver- 

 age weight is given in terms of 1,000 seeds instead of in terms of a 

 single seed. 



It will be seen that in every instance the size of the seed was mate- 

 rially increased by the foreign pollen. The increase ranges from 2.8 

 to 21.1 per cent. It should also be noted that the rate of increase 

 bears no direct relation to the size of seed in the variety used as the 

 source of pollen. The seeds of the Algeria variety average only half 

 as heavy as those of Mexico Black, yet the increases secured when 

 Algeria is used as the source of pollen are rather greater than when 

 Mexico Black pollen is used. 



Table I. — Increase in size of seed secured by cross-pollination. 



Ear-bearing plant. 



Variety. 



Pipe. 



Gracillima . 



Variegated 



Hickory King. 



No. 



259 



2.39-2 

 267 



1212 

 1220 



I22>-2 

 122>3 



1227 



1227-2 

 1228 



219 



Source of the mixed pollen. 



White. 



Variety. 



Self. 



Pipe. 



Self. . 



..do. 

 ..do. 



Gracillima 

 ...do 



Self 



Variegated 

 ...do...... 



Self 



Plant 

 No. 



267 



1212 

 1212 



1228 

 1227 



Colored. 



Variety. 



Mexican 

 Black. 



...do 



...do 



Algeria 



Mexican 

 Black. 



...do 



Algeria 



Mexican 

 Black. 



...do 



...do 



...do 



Plant 

 No. 



643 



643 

 643 



1301 

 669 



669 

 1301 



653 



653 

 &53 



643 



Number 

 of seeds. 



Pure. 



511 



541 

 553 



171 

 99 



350 

 139 



402 



111 

 496 



140 



Hy- 

 brid. 



220 



248 

 2J 



235 

 211 



94 

 175 



81 



24.5 



2.5 



104 



Weight per 

 1,000 seeds. 



Pure. 



Grams. 

 294 



268 

 371 



65 

 74 



66 

 65 



137 



140 

 144 



522 



Hy- 

 brid. 



Grams. 

 337 



293 

 420 



79 

 80 



74 



74 



1.56 



148 



148 



557 



Increase 

 with cross- 

 pollination. 



Per cent. 

 14.6 ±0.7 



9.3 ± 1.0 

 13. 2 ± .6 



21.1 ± .9 

 7.9 ± .8 



12.3 ±1.4 



13. 8 ± 2. 1 



13.9 ±2.2 



5. 7 ± .6 

 2.8 ± .9 



6. 7 ± .2 



LCir. 124] 



