Nov. 1913.] Microsporocytes 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 microsporocytes the chromatin 
material is scattered throughout the nucleus on a loose reticulum. 
2. There are seven protochromosomes formed, some of which 
show a double nature. 
3. These protochromosomes are transformed into a spirem. 
4. There is a period of contraction or svnizesis 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. Davis, B. M. Cytological Studies in Oenothera I. Pollen 
Development of Oenothera grandiflora. 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. Gates, 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 Cvtologie und der 
parteilen Sterelitat von Oenothera Lamarckiana. Recueil 
des Travaux Botaniques Neerlandais, 5: 93, (Reprint 1-114) 
1909. 
8. McAvoy, Blanche. The Reduction Division in Fuchsia. 
Ohio Naturalist, 13 : 1—IS. 1912. 
