ipoS] NICHOLS— POLLEN OF SARR.ACENLA 33 



nucleus, as if it had been accidentally displaced in cutting the section 

 (fig. 28). If this be true, it would seem to indicate that the nucleolus 



independent in structure and 



OWTl. 



pirpureGy two nucleoli are found 



than the other (fig 



ed 



fl. 



appears dark, the peripheral portion lighter, while from the central 



ifii' 



stain 



(Jig. zf). The chromatic 



fine granule 



linin fibrils {jig. 27). At this stage the nucleolus, in preparations 

 stained with safranin and malachite green, colors purple, inclosing 



eranules 



The nucleoli of the 



tapetal cells, on the other hand, stain red. 



The conversion of the network into chromosomes during the pro- 

 phases of the first maturation di\dsion is illustrated in Jigs. 2g-ji. 

 A longitudinal splitting of the chromatin granules and linin fibers 

 is clearly seen, the halves thus formed often showing a tendency to 

 spread apart (fig. 30). The chromosomes occur in pairs, which come 

 to lie parallel to each other (figs. 29-31) . They gradually shorten 

 and thicken, so that finally little difference is evident between the 

 length and breadth. That the spindle is formed, at least in part, 



linin fibers would appear from fig 



\ 



rtry late prophase. The spindle fibers when fully torm( 

 defined and show minute swellings. Two fibeK may be 

 to a chromosome in fig. 33. The separati 



are 



somes IS 



fig. 34. The U-shaped 



some would seem to correspond to the more elongated body of similar 

 shape in fig. 29, and if this is true the first division separates univalent 

 chromosomes and is reducing. The nucleolus persists at its fuU size 

 until a late prophase. The total number of chromosomes in 5. varia- 

 laris and in S. rubra is ac 



5. rubra is apparently twelve. The material did not 



, ^js suitable for determining the number in the other 



species studied. Shre\t: (10) reports twelve in 5. purpurea. 



After the first division of the chromatin, the daughter nuclei 

 tJT^.derso no reconstruction, but arrange themselves for the succeedm 



^v^ i^vy ^^vw^i^^^^v-v^^.^3 



mitosis {fig. 



The chromosomes seem to become somewhat 



