BoT.— Vol. II.] OSTERHOUT— AGAVE. 26g 



the number is usually not less than four or more than ten. 

 Not all the fibres are used in the formation of cones, since 

 some remain, like the exterior fibres of the first division, 

 radiating out into the cytoplasm after the cones are fully 

 formed (fig. 23). 



The disappearance of the nuclear wall begins, as is 

 usually the case, under one of the cones, and gradually 

 continues under first one and then another of the remaining 

 cones until complete. The genetic fibres penetrate rapidly 

 into the interior of the nucleus and become attached to the 

 linin network, which increases rapidly during cone forma- 

 tion (fig. 23, lower half). 



The details of the process just described are extremely 

 variable. Sometimes the formation of the genetic fibres is 

 greatly delayed, and scarcely anything can be seen of such 

 fibres until just before the nuclear wall breaks down; then, 

 however, they appear to be formed very rapidly. In such 

 cases the cones do not usually reach the size shown in 

 fig. 23. 



During the genetic stage the nucleolus disappears com- 

 pletely while the linin increases in amount (fig. 23). 



From the figures it will be seen that while in general the 

 process of spindle formation goes on simultaneously in 

 both daughter cells, this does not quite hold true of such 

 stages as are shown in figs. 22 and 23. This is probably 

 to be accounted for by the fact that these stages are passed 

 through with extreme rapidity. These remarks apply par- 

 ticularly to the assemblage of the fibres into cones and the 

 breaking down of the nuclear wall. The stage shown in 

 fig. 23, upper half, is not passed through quite so rapidly, 

 and it is more common to find both daughter cells in this 

 stage at the same time. 



4. Stellar Stage. 



The stellar stage is variable in length and presents con- 

 siderable diversity as regards the form of the spindle and 

 the number of cones composing it. Frequently the cones 



