228 Atkinson. 



final arrangement and relation as cell wall formation and the morpho- 

 genic processes begin in the embryo were not determined. Strasburger 

 (20, 1904) attempted to study the nuclear spindle for the f^rst division 

 in the fertilized egg and the organization of a working relation of the 

 chromosomes in Funkia and Oaltonia, where the chromosomes are of 

 different sizes, but was unable to accomplish the desired result because 

 of the rarity of seed formation. While he has observed several division 

 stages in the fertilized egg in Iris sihirica and Triticum vulgare, he 

 discovered nothing unusual. The difficulties met with in the study of 

 the cytological processes of the first division of the fertilized egg in 

 plants appear to be very great. But tliis should not deter plant cyto- 

 logists from undertaking the problem, for it is an important and critical 

 stage in the life cycle of plants which deserves investigation. 



While our knowledge of the behavior of the paternal and maternal 

 nuclei in the fertilized egg is so meager that we cannot build upon it 

 with any great degree of assurance a theory of the organization of hy- 

 brids from the union of the parental characteristics represented in the 

 egg and sperm, several hypotheses of segregation into distinct hybrid 

 types may be considered. 



1 St. Is the production of twin and triplet hybrids due 

 to the mutating condition of one of the parents? According to 

 de Vries (109, 1913) segregations in the first generation are the result 

 of peculiar, or real, mutation crosses. These were first described by 

 de Vries (1907) in crosses when certain wild species of Oenothera from 

 the sand dunes of Holland, Oe. biennis, Oe. muricata, were employed as 

 the mother, and Oe. Lamarckiana or certain of its mutants were used 

 as the pollen parents. Two types of hybrids are obtained in the first 

 generation from such crosses. These he designates "twin hybrids". 

 Both are intermediate hybrids, but on close inspection are found to be 

 quite distinct. One has broad flat leaves of a bright green and is 

 named Oe. laeta. The other has narrow, furrow -shaped leaves of a 

 grayish green and is more hairy. This is Oe. velutina. The laeta 

 strongly resembles Lamarckiana, the pollen parent, while velutina strongly 

 resembles the mother {biennis or muricata as the case may be) or, 

 rather, strongly resembles the ''egg cell type" or ''egg cell constitution" 

 of the mother (See de Vries, 74 — 84, 1913). Further examples of se- 

 gregation in the first generation with the formation of twins, and even 

 triplets and quadruplets, were described by de Vries in 1909 and 1913, 

 in which laeta and velutina tj'pes, as well as other tjrpes, appear. 



