Gates.—Pollen Formation in Oenothera gigas . 937 
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EXPLANATION OF PLATES LXVII-LXX. 
Illustrating Dr. Gates’s paper on Pollen formation in Oenothera gigas. 
(The lenses used were a Leitz inch oil immersion, ap. 1-40 with compensating oculars, the 
figures being reduced one-fourth in reproduction. This gives magnifications which allow comparison 
of the size of the cells in O. gigas with those of other Oenotheras figured in my previous papers.) 
PLATE LXVII. 
Fig. 1. Archesporial pollen mother-cell just previous to the beginning of synapsis. Many dark 
bodies appear near the periphery of the nucleus, x 2,850. 
Fig. 2. Nucleus showing the beginning of synapsis. The nuclear membrane is gradually 
expanding and being pushed away from the reticulum, x 2,850. 
Fig. 3. Mother-cell in the beginning of synapsis. Apparently a rather explosive rupture has 
taken place on one side of the nucleus, producing a cavity in the cytoplasm filled only with karyo- 
lymph. The cytoplasmic reticulum presents a rather ragged appearance. No change has yet taken 
place in the nuclear reticulum, x 2,850. 
Fig. 4. A slightly later condition, in which the distension of the nuclear membrane has been 
followed by its rupture at one place, producing an ill-defined area in the cytoplasm on the right side 
filled with cell-sap. On the left side a few nuclear threads remain attached to the membrane, x 2,850. 
Fig. 5. Synapsis is nearly completed. A single nucleolus is enclosed in the meshes of the 
delicate threadwork, which is nearly transformed into a spireme. The nuclear membrane is very 
indistinct on one side and the cytoplasmic reticulum is ‘ ragged \ x 2,850. 
Fig. 6. Pollen mother-cell in synapsis (synizesis). The nuclear threads are extremely attenuated. 
The nuclear membrane is intact and the cytoplasmic reticulum is not ragged, x 1,875. 
Fig. 7. Same synaptic condition as Fig. 6. Darker areas appear on the nuclear threadwork, 
which is quite transformed into the spireme condition. The nucleolus is attached to the nuclear 
membrane, x 1,875. 
Fig. 8. Row of pollen mother-cells, showing the extrusion of chromatin from the nucleus of one 
mother-cell into the cytoplasm of the next, to form pseudo-nuclei, x 600. 
