12 



was pul)lished, which reforred to the saino phononienon. In this very 

 inttM'cstino- jviid suggestive article a nuinl)er of premises or propositions 

 regarding the immediate influence of pollen in maize were given, but 

 without an account of the experimental evidence on which they were 

 based. From his experience Correns concludes that almost all races 

 of Zea mays are capable of being modified in at least one character by 

 fecundation with pollen from another race, and conversely that almost 

 all races are in condition to lie directly modified by at least one other 

 race in at least one character. The most important features of 

 Correns's conclusions are the following: 



1. The influence of the foreign pollen exhibits itself only in the endosperm, all 

 partf: which are outside of this remaining entirely uninfluenced. 



2. The influence extends only to the color of the endosperm and the chemical 

 composition of the reserve materials — the starch or dextrin therein. In all cases 

 the size and form of the kernels remain unchanged. 



Previous to the discover}^ of the process of double fectindation by 

 Nawaschin and Guignard, Correns came to the conclusion that either 

 the secondary nucleus of the embryo sac must fuse with one of the 

 generative nuclei from the pollen tube or that the effect was due to an 

 enzymatic influence from the h3^])rid embryo. The former view, he 

 decides, is proved to be correct by the actual discovery of double 

 fecundation. 



The supposed immediate effect of pollen in other plants than maize 

 has been frequently reported, the influence extending not only to the 

 endosperm, Init apparently to the seed coats and pericarp. The effect 

 of foreign pollen on the color of the seed coats of peas was inferred 

 as early as 1729 and repeatedly since then, being reported b}^ such 

 experimenters as Gaertner and Berkeley. Laxton stated that he had 

 observed an effect of foreign pollen not only on the color of the seed 

 coats, but also on the pod in some instances, and his observations were 

 confirmed b}^ Darwin so far as tho color of the seed coats was con- 

 cerned. In 180;^ Dr. Giltay^ published an account of the results 

 obtained ])v him from quite immerous experiments in crossing differ- 

 ent varieties of peas which had been selected particularly to demon- 

 strate whether xenia occurs in these plants. He made crosses of 

 fifteen different com])inations, obtaining from ten to twentj^-five seeds 

 of each, and also grew lumierous control plants to demonstrate that 

 the seed used was pure. From his experiments he concludes that 

 the influence of the pollen is not shown outside of the embryo. The 

 influence of the cross, however, was plainly manifested in the color 

 of the cotyledons, which in numerous instances showed very plainly 

 through the colorless coats of the seed, so that unless carefully 

 examined it might be assumed that the seed coats themselves were 



^Giltay, E. Ueber den directen Einfluss des Pollens auf Frucht und Samenbil- 

 dung. Jahrb. f. wissensch. Bot.,Bd. 25, p. 489. 1893. 



