COLLINS AND KEMPTONI A NEW HYBRID 



115 



it is difficult even to contrast the characters. The following is 

 an attempt to formulate the more conspicuous differences: 



Tripsacum 



Plants perennial. 



i\Iale and female flowers in the same 

 inflorescence. 



Lateral inflorescences not enclosed in 

 bracts. 



Fruit trapezoidal. 



Order of flowering of pistillate flowers 

 from above downward. 



Staminate spikelets in pairs, both ses- 

 sile. 



Leaves averaging about 50 times as 

 long as wide. 



Euchlaena 



Plants annual. 



Male and female flowers in different 

 inflorescences. 



Lateral inflorescences enclosed in 

 bracts. 



Fruit nearly triangular. 



Order of flowering of pistillate flowers 

 from near the bottom upward. 



Staminate spikelets in pairs, one ses- 

 sile, the other pediceled 



Leaves averaging about 10 times as 

 long as wide. 



Euchlaena and Tripsacum are the only American genera as- 

 sociated with Zea in the tribe Maydeae. Euchlaena and Zea 

 cross readily and a complete series of intermediates is known. ^ 



Although the possibility of securing a hybrid between such 

 diverse plants seemed verj^ remote, the paucity of wild relatives 

 encouraged us in repeated attempts to secure hybrids between 

 Tripsacum and Zea or Euchlaena. Until the present instance 

 these attempts have always given negative results.-* 



The pollen parent of the present hj^brid belonged to a Mexican 

 variet}^ of Euchlaena, the seed of which was received from Mr. 

 H. A'. Jackson of Durango, Mexico. This variety is earlier 

 than the Florida teosinte and many of the plants show indica- 

 tions of contamination with maize. Among the most common 

 maize-like characters occurring in the teosinte from this region 

 are the development of a central spike in the staminate inflor- 

 escence, the greater prominence of the primary culm, and the 

 formation of a rudimentary cob in the pistillate inflorescence. 



^ For a discussion of the characters of Euchlaena and Zea, see Collins, G.X., 

 The origin of maize, Journ. AVash. Acad. Sci. 2: 520-530, 1912. 



■• In view of the great disparitj' in the length of the stigmas, there may be 

 a mechanical difficulty in making the reciprocal cross, using Tripsacum as the 

 pollen parent. 



The maximum elongation of the pollen tube in fertilizing Tripsacum flowers 

 would never exceed 2 cm., while the fertilization of an ovule of Zea or Euchlaena 

 could not be accomplished without an elongation of at least 10 cm. 



