Box.— Vol. II.] HUS— CASSIA TOMENTOSA L. 345 



denener Fadenknauel erscheint. Eine nahere Untersuch- 

 ung feinster Schnitte zeigt jedoch, dass diese Filzschicht 

 aus der Kernwandung parallel in die Lange gezogenen 

 Schlingen (Maschen) besteht." 



This description would fit the felt-like zone occurring in 

 the pollen-mother-cells of all the plants just mentioned; but 

 Belajeff's words, " Die obenbeschrieben Umgruppirung der 

 Plasmafaden ist, wie es scheint, die Folge ihrer Contraction 

 und des Zusammenziehens der Schlingen (Maschen) um 

 den Zellkern," do not agree with the views of others in 

 regard to this matter. Both Byxbee and Williams are of 

 the opinion that the meshes become elongated because of a 

 drawing-out. This then would be caused, not by a con- 

 traction of cytoplasmic threads, but by their expansion. 

 What causes this expansion is not yet explained, but an 

 increase in size of the nucleus is not improbable, and how- 

 ever slight, would produce the appearance described. 

 Observations on Cassia tend to confirm this supposition. 

 But whatever the manner of its origin, a weft-like zone 

 seems to be formed around the nucleus in nearly all cases. 



The manner in which the fibers of cytoplasmic origin 

 form cones seems to differ in the various plants observed. 

 In this connection it is necessary to call attention to the 

 fibers which may be seen in the cytoplasm at the time of the 

 formation of the fibrous zone. In C«ssm these fibers appear 

 when the first changes in the cytoplasm immediately adjoining 

 the nucleus begin to take place. At various points the 

 presence of granular fibers, which stain a deep violet and 

 which are sometimes arranged in conical groups, be- 

 comes apparent. They remind one of the "irregular, 

 deeply staining strands" of /'«55?)?ora( Williams, 1899, p. 191) 

 or of the cones of Equisetimi (Osterhout, 1897, p. 161, fig. 

 4). In Cassia these fibers apparently establish a connection 

 with the fibers of the fibrous zone, which latter gradually 

 become parallel, or nearly so, to the thicker granular fibers 

 running at a greater or lesser angle to the nuclear wall. 

 The origin of the cones is apparently determined by the 

 thicker granular fibers. No drawing-out of the cones takes 

 place. 



( 2 ) April 15, 1904. 



