Nov. 1913.] Mierosporocytes of Oenothera Biennis. 193 



bodies of the same general shapes as appear in the first division 

 but much smaller. The tetrad (Fig. 34) appears normal, irregu- 

 larities not being so abundant as in Fuchsia. 



SUMMARY. 



1. In very early stages of the mierosporocytes the chromatin 

 material is scattered throughout the nucleus on a loose reticulum. 



2. There are seven jirotochromosomes fornied, some of which 

 show a double nature. 



3. These protochromosomes are transformed into a spirem. 



4. There is a period of contraction or synizesis during which 

 loops of the spirem project out from the contracted mass. The 

 spirem shows a granular nature. 



5. The spirem is continuous and becomes thrown into loops 

 seven of which are shown in many preparations. 



6. These seven loops contract until seven separate bivalent 

 chromosomes are formed. About this time the nuclear mem- 

 brane disappears. 



7. The univalent chromosomes remain as seven distinct 

 bodies in the daughter nucleus and are easily distinguishable until 

 the beginning of the second division. 



8. The second division follows and results in the formation 

 of normal tetrads. The seven chromosomes are again easily 

 counted in this division although they are much smaller. 



LITERATURE CITED. 



1. D.wis, B. M. Cytological Studies in Oenothera I. Pollen 



Development of Oenothera grandifiora. Ann. of Botany, 

 23: 551-571. 1909. 



2. Davis, B. M. Cytological Studies of Oenothera II. The 



Reduction Division of Oenothera biennis. Ann. of Botany, 

 24:631-651. 1910. 



3. G.A.TES, R. R. Pollen Development in Hybrids of Oenothera 



lata X Oenothera lamarckiana, in its Relation to Mutation. 

 Botanical Gazette, 43: 81-115. 1907. 



4. Gates, R. R. A Study of Reduction in Oenothera rubri- 



nervis. Botanical Gazette, 46: 1-34. 1908. 



5. Gates, R. R. The Stature and Chromosomes of Oenothera 



gigas De Vries. Archiv. fur Zell forschung. 3: 525-552.1909 



6. Gates, R. R. The Behavior of Chromosomes in Oenothera 



lata X Oenothera gigas. Botanical Gazette, 48: 179-199. 

 1909. 



7. Geertz, J. M. Beitrage zur Kenntnis der Cj'tologie und der 



parteilen Sterelitat von Oenothera Lamarckiana. Rccueil 

 des Travaux Botaniques Neerlandais, 5: 93, (Reprint 1-114) 

 1909. 



8. McAvoY, Blanche. The Reduction Division in Fuchsia. 



Ohio Naturalist, 13: 1-18. 1912. 



