226 MAINE AGRICULTURAL EXPERIMENT STATION. 



imprint of its character on the female organism, which shall be 

 dififerent from that of a less vigorous male parent. It is prob- 

 able, however, that the vigor and inherent vitality of the plant 

 operated upon may determine whether this be manifested. Some 

 species show apparently unmistakable evidences of the influence 

 of foreign pollen, — this is notably true of peas and Indian corn. 

 On the other hand, cucurbitaceous and solanaceous plants seem 

 to resist all foreign influences ; while rosaceous plants are in dis- 

 pute, with the weight of authority tending to show the absence 

 of immediate influence." This point will be the subject of 

 special attention during the present year. 



The Stimulating Influence of Pollen. — Focke says, "Pollen has 

 two actions on the female organs, one on the seeds and one in 

 exciting the growth of the fruit."* 



It is a matter of common observation that, as a rule, when 

 pollination fails to result in fertilization, or when pollen is with- 

 held, not only the pistil withers, but the entire flower decays and 

 falls. Instances are not infrequent, how^ever, wdiich point to a 

 responsive action on the part of the pistil or other portions of 

 the flower receiving pollen, while from an insufficient quantity 

 of pollen, lack of affinity on the part of the species crossed, or 

 some other cause which remains to be determined, fertilization 

 does not occur. Examples of this are specially common in all 

 of our cultivated fruits and vegetables, particularly garden 

 beans and in the English forcing cucumber, shown in figures 9 

 and 5, respectively. 



The pepino, Solanum nnmcatuni, (fig. 7), is also a case in 

 point. This plant blooms profusely and, under proper condi- 

 tions, sets a considerable amount of fruit, which, however, is 

 invariably seedless. The writer has made repeated attempts to 

 cross this species with other solanums but thus far without 

 success. 



Since the work of Koelreuter in 1765,! little has been done 

 toward determining the actual amount of pollen required for 

 the fertilization of any given species ; but in our own work the 

 fact that the amount of pollen applied may have great practical 

 importance in determining form and size of the fruit, as well as 



* Die Pflanzen mischlinge, 447. 



t Cited by Sachs, Hist, of Botany, 408. 



