INTRODUCTION 5 



(1750) had a pistillate palm in Berlin which was 80 years old 

 and had set no seed. He obtained a quantity of pollen from 

 trees in Leipsic (then nine days' journey from Berlin) and after 

 pollination seed was produced which germinated. 



The Studies of Koelreuter. 1 While these investigators and 

 others confirmed the work of Camerarius, little advance was made 

 in the art of breeding until Koelreuter (1761) made a careful 

 study of artificial crosses and gave the first extended account. 

 In tobacco crosses, for example, he found that the first generation 

 was of intermediate habit and therefore showed the effect of the 

 male parent. His work on the vigor of first generation crosses 

 is of much interest. He believed the "oil" of the pollen grain 

 after mixing with the stigmatic fluid penetrated the ovule. The 

 belief of a union of male and female substances was a step in 

 the right direction. The value of insects as carriers of pollen 

 was also demonstrated. 



Early Studies in the Cytology of Fertilization. Pollen tubes 

 were first observed in 1823 by Amici who followed them to the 

 micropyle of the ovule in 1830. Schleiden shortly afterward 

 made numerous studies of the pollen tube and apparently thought 

 the embryo developed in the embryo sac from the end of the 

 pollen tube. This matter was not thoroughly cleared up until 

 Strasburger (see Johnson, 1915) concluded, in 1884, that: 



"1. The fertilization process depends upon the copulation with the 

 egg nucleus of the male nucleus which is brought into the egg. 2. The 

 cytoplasm is not concerned in the process. 3. The sperm nucleus, like 

 the egg nucleus, is a true cell nucleus. " 



An Answer to the Question of Hybrid Fertilization. Al- 

 though Koelreuter proved the fact of sexuality in plants it 

 was not generally accepted, and early in the nineteenth century 

 the Physical Section of the Royal Prussian Academy offered a 

 prize for an answer to the question, "Does hybrid fertilization 

 occur in the plant kingdom?" Among other results presented 

 by Weigmann in answer to this question occurs the statement of 

 the immediate effect of pollen in legumes. Weigmann made a 

 study of 36 crosses using the following plants: onion, cabbage, 

 pea, bean, lentil, pink, and tobacco. He observed the fact of 

 variability due to crossing and thought gardeners should pay 



1 For these facts the papers of other writers have been freely used. Those 

 by ROBERTS (1919) have been especially helpful. 



