THE ORIGIN OF NEW VARIETIES. 



without bringing about the extrusion of the stamens and stigma. 

 At Arlington Farm, during the season of 1909, a few of the flowers 

 had their stamens and stigmas extruded. Whether such extrusion is 

 due to insects or not remains to be determined. It has never been 

 observed in the hundreds of plants grown in the Department green- 

 houses. 



THE ORIGIN OF NEW VARIETIES. 



The fact of the existence of numerous varieties of cowpeas calk 

 for some explanation of their origin. Mention has already been 

 made (p. 15) of the fluctuations or fluctuating variations so marked 

 in the cowpea. It is now the general belief that such variations 

 are not hereditable in any plants, and if such is true this type of 

 variation can have had no effect in producing the large number of 

 varieties which exist. A second method by which new varieties 

 arise is that commonly spoken of by gardeners as " sports," that is, 

 the sudden origin of a form differing markedly from all others. 

 There can be no question as to the occurrence of what are termed 

 " bud sports " ; that is, where one branch of a plant bears flowers 

 or leaves different from the other portion, which can be propagated 

 and maintained by cuttings. As to the occurrence of true sports 

 among seedlings, the evidence is not so absolute ; but it is the common 

 belief that such seed sports do occur and that they usually breed true. 

 A third method by which new varieties are believed to originate 

 is that of gradual variation, which differs from sporting only in 

 that the variations are slight, though they tend to continue in the 

 direction started. The fourth method is that of hybridization. 

 There is no question whatever that new varieties can be originated 

 by the crossing of two old varieties, and a very large number of 

 cultivated varieties not only of the cowpea but of other plants are 

 known to have originated in this way. It is evident, however, that 

 there can be no hybrids until at least two distinct varieties exist, and 

 it is, therefore, absolutely necessary first to admit the origin of the 

 primitive varieties either by sporting or by gradual variation. 



Thus far there is no satisfactory proof of the existence of either 

 sports or of gradual variation in the cowpea. It is clear that such 

 evidence can be obtained only by growing pure cultures of varieties 

 under conditions where hybridization or accidental admixture of 

 seeds is out of the question. 



Nevertheless, it seems reasonably certain that a considerable num- 

 ber of the American varieties of cowpeas have originated in this 

 country; at least, many of them have not been found in the very 

 numerous importations made from abroad, though varieties closely 

 similar in their seed characters have been obtained. As an example, 



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