2 BULLETIN 971, U. S. DEPAKTMENT OF AGRICULTURE. 



While the pistillate inflorescence is entirely branched, none of the 

 other characteristics of a normal ear are altered. The glumes are 

 membranaceous and inconspicuous, the spikelets are paired and prac- 

 tically sessile, one flower only is developed in each spikelet, and there 

 is no indication of the development of stamens. The branches bear 

 four rows of spikelets, being similar in this respect to the branches 

 of a tassel. The ramose ear, therefore, may be considered as a rever- 

 sion to a more primitive type in only the one character of branching. 



Accompanying the ramose pistillate inflorescence is an almost 

 equally striking alteration in the form of the staminate inflorescence. 

 (See Pi. XIII.) In normal maize the tassel has a few branches at 

 the base and terminates in a single upright spike bearing four or 

 more rows of paired spikelets. This terminal spike usually exceeds 

 half the length of the entire inflorescence, and in some varieties its 

 relative length is much greater. The transition from branches to a 

 single central spike is abrupt, the upper and lower branches being 

 of nearly the same length. In the ramose type of tassel the branch- 

 ing is continuous, extending from the base to within a few centi- 

 meters of the apex, leaving a very short central spike, while the 

 total number of branches in extreme cases exceeds 400. These 

 branches decrease gradually in length until they consist of but three 

 or four spikelets on rather elongated pedicels, with an almost im- 

 perceptible transition from branches to pairs of spikelets. 



As with the ramose ear, the tassels with their large number of 

 branches produce a far larger number of spikelets than the tassels 

 of commercial varieties, and also a greater amount of pollen. The 

 whole tassel has a distinct conical shape quite unlike that of the 

 normal form. 



Since the ear of the Ramosa variety is branched in a manner 

 similar to the tassel, with an absence of a predominating central 

 spike, it would seem reasonable to conclude that the differentiation 

 of the sexes in maize occurred before the loss of the lateral branches, 

 and the central spike of the tassel may be assumed to have developed 

 simultaneously with the single-spiked ear. 



While the ramose type of inflorescence has been found to segre- 

 gate as a unit in crosses with the normal form (1), no evidence has 

 been presented to show whether this seemingly simple Mendelian 

 character has suffered any alteration as a result of such hybridiza- 

 tion and, further, whether the normal plants segregating from 

 ramose hybrids have undergone changes in the structure of the 

 inflorescence. 



The opportunity to measure the effect of hybridization on Men- 

 delian characters is unique in Ramosa X normal crosses. The ramose 

 variation is large, affecting both staminate and pistillate inflores- 



