48 MAINE STATE COLLEGE 



Another instance of the partial developnent of the ovary was 

 observed in a Summer Crookneek squash to which pollen of an- 

 other ■ variety was applied by Professor Bailey, at the Cornell 

 University. The fruit attained about eight inches in length, and 

 remained in this condition during the season. No perfect seeds 

 were developed. 



From the evidence adduced the fact seems well established that 

 in certain species, the ovary may develop and reach normal size 

 without the corresponding impregnation of the ovules, and even 

 in the entire absence of the male element. What the conditions 

 are which induce this apparently abnormal condition, is not ful- 

 ly determined. It is evident, however, that vigorous growth of 

 the parent plant is of first importance. 



III. On the Amount of Pollen Required for Fertiliza- 

 tion ; AND the Effects of Pollination on the 

 Form and Size of the Fruit. 



Koelreuter, in 1761-66, found that witli Hibiscus venetianus 

 fifty to sixty pollen grains were sufficient to produce more than 

 thirty fertile seeds in the ovary. In Mirahilis jalapa^ and M. 

 longijlora, which have a one ovuled ovary, two or three, and in 

 some cases even one grain was sufficient for fertilization. | Now, 

 according to Koelruter, the Hibiscus produced 4863 pollen grains 

 in a single flower, — or eighty-one times more than needed for 

 actual fertilization. So also the Mirablis produced about 300 

 grains, or from 100 to 200 times too much. It appears therefore 

 that there is no relation between the amount of pollen produced 

 by a plant, and the amount required for fecundation. 



Since the time of Koelreuter, little has been done toward deter- 

 mining the actual number of grains required for the fertilization 

 of any given species ; but the fact has been plainly demonstrated 

 that the amount of pollen applied may have great practical im- 

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

 the quantity of fruit produced. 



In crossing strawberries at the New York Agricultural Experi- 

 ment Station, the fact was plainly brought out,| that the propor- 

 tion of berries secured depends upon the abundance of the pollen 



tCited bj- Sachs, Hist, of Bot. 408. 

 jsth An. Rep. >'. Y. Exp. Sta. 179. 



