32 



Journal of Agricultural Research 



Vol. XIX, No. I 



There are also significant coherences with number of ahcoles and node 

 silking first. The disherent correlations with male secondaries and 

 length of intemode on third appear to be genetic. That with length of 

 internode on third is the highest coefficient with 

 1 days to pollen. 



^^ 





/^ 



POLLEN TO SILK 



^ Maize is normally proterandrous. There are, 



^ however, proterogynous strains of maize, and pro- 



terogynous individuals in almost any strain are 

 not uncommon. Tom Thumb is normally proter- 

 androus by about lo days, Florida teosinte ap- 

 pears to be normally proterogynous. It has always 

 been so in our experiments; and an examination of 

 the fields at Clarcona, Fla., in 1914, showed the 

 plants to be silking from 7 to 10 days before pollen. 

 Durango teosinte, on the other hand, under most 

 conditions is proterandrous. 



In both maize and teosinte this character is es- 

 pecially susceptible to environmental influence. 

 The Fj plants were decidedly proterandrous at 

 both Lanham and Chula Vista. None of the Fg 

 plants w^ere proterogynous, the proterandry rang- 

 ing from o to 53 days, with the mean at 18.3. 

 The distribution (fig. 32) was symmetrical and 

 unimodal. 



There are but two significant correlations with 

 this character, both coherences. These are with 

 circumference index and position of best spike. \)^o 

 The latter is in one sense physiological. • 1^ 



Fig. 32. — Pollen to silk: fre- 

 quency distribution of plants 

 in Fa. Class value, five days. 



30 



/O 



LENGTH OP INTERNODE ON THIRD 



This character was determined by dividing the 

 length of the third branch by the number of in- 

 temodes. The branches from the upper nodes of 

 a maize plant are much shortened. An accurate 

 measure is impossible on account of the difficulty 

 of accurately determining the number of nodes. 

 In Tom Thumb it would, however, be somewhat 

 less than i cm., and in normal maize plants of any 

 variety it would scarcely exceed 3 cm. In a nor- 

 mally developed teosinte plant the internodes of 

 the third branch will average about 10 cm. This 

 character was not recorded in the first genera- 

 tion. In the F2 plants the mean was 10.9 cm. The range was from 

 2 to 22, with practically a normal distribution (fig. 33). 





Fig. 33. — Length of internode 

 on third: frequency distri- 

 bution of plantsinFj. Class 

 value, 2 cm. 



