A BRACHYTIC VARIATION IS MAIZE. 9 



branch immediately below until the uppermost branch, borne in the 

 axis of the second leaf from the top, has but two nodes. Thus each 

 branch has one more internode than has the portion of the main culm, 

 which is immediately above it. Contrary to Montgomery (13), this 

 does not hold true for maize, but the relation may have been modified 

 through brachysm. There is some evidence to show that the total 

 number of nodes is increased when the main culm is brachytic, and if 

 this fact held true for lateral branches it would account for the differ- 

 ence between maize and teosinte in this respect. When the ear stalk 

 is lengthened, as in the tropical varieties previously mentioned, it be- 

 comes possible to ascertain the number of nodes with accuracy. In 

 these cases it has been found that there are 15 or more nodes, while 

 only 5 or 6 nodes of the main stalk are above the ear-bearing branch. 



Although the pistillate inflorescence of maize affords the most 

 striking example, there are indications of brachysm in the formation 

 of the male inflorescence. If it is assumed that the internodes of the 

 main axis are shortened and the terminal spike is formed through a 

 reduction of lateral branches, this would constitute a still further 

 stage of brachysm. 



Brachysm of the main culm might be considered an example of 

 homoeosis (12), but on this hypothesis it is difficult to understand the 

 absence of any tendency for the brachysm of the upper branches to 

 become transferred to lower ones, a step much more direct than that 

 involved in transferring this characteristic to the main culm. There 

 is, however, some support for this view in that several of the 

 brachytic j)lants developed pistillate flowers in the otherwise unal- 

 tered staminate inflorescence, and although none of these pistillate 

 flowers developed seed this fact suggests that an association exists, 

 however slight, between brac}i;ic internodes and the development 

 of female flowers. 



ASSOCIATED CHANGES. 



Mutations in most organisms are not confined to single characters, 

 but alter the expression of many and frequently unrelated parts. 

 Usually a particular character is changed greatly, serving to divert 

 attention from minor changes in other characters. Careful examina- 

 tion of many characters of an individual which has mutated obvi- 

 ously in a single one often reveals the presence of the other changes. 



With the intention o-f determining whether other characters than 

 internode length had undergone alteration in the original brachytic 

 plants, careful measurements were made of other organs. Only two 

 other changes were observed. The ears were flattened somewhat, 

 doubtless due to the mechanical pressure of the large number of leaf 

 sheaths. Such an alteration can not be considered as mutative, since 

 it is an indirect manifestation of the brachytic condition. The other 

 16071°— 21 2 



