738 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



have been Lawson ('98) on Cobea, W. C. Stevens ('98^) on 

 Asclepias, Atkinson ('99) on Arissema and Trillium, Duggar 

 ('99) on Bignonia, Wiegand ('99) on Convallaria and Potamoge- 

 ton, Gregoire ('99) on Lilium and Fritillaria, Guignard ('99) on 

 Naias, Williams ('99) on Passiflora, Duggar (: 00) on Symplo- 

 carpus and Peltandra, Lawson (: 00) on Gladiolus, Byxbee (: 00) 

 on Lavatera, Andrews (: 01) on Magnolia and Liriodendron, 

 Schniewind-Thies (:0i) on Galtonia and Osterhout (: 02) on 

 Agave. 



Of the papers listed above several demand especial attention 

 for the completeness of the studies on the early stages of spindle 

 formation in the pollen mother-cell. Lawson ('98 and : 00) 

 found that the nuclei of Cobea and Gladiolus previous to mitosis 

 were surrounded by a zone of granular kinoplasm which he 

 named perikaryoplasm. This zone developed a felted envelope 

 of fibrillcB from which projections extended to form the cones of 

 a multipolar figure. The cones by fusing in two groups devel- 

 oped the bipolar spindles. The spindle fibers of Gladiolus are 

 formed entirely from the perikaryoplasm, the nucleolus and linin 

 apparently taking no part in the development of the spindle. 

 , The nucleolus remains intact until after the dissolution of the 

 nuclear membrane when the spindle is practically completely 

 organized. Miss Williams ('99) found for Passifloi^a that the 

 nuclear cavity became filled with a network developed from the 

 linin. The nuclear wall became also transformed into a mesh 

 which connected the network from the linin with the surround- 

 ing cytoplasmic reticulum, thus forming a continuous system 

 throughout the cell. The central region of this network, 

 enclosed by a granular zone, developed a multipolar figure 

 whose poles finally fused to form a bipolar spindle. The con- 

 trast between this type of spindle in which so much of the 

 fibrous structure is derived from the linin and that of Gladiolus 

 just described is very marked. A granular region outside of 

 the fibrous network around the nucleus is much more conspic- 

 uous in Lavatera, described by Byxbee (: 00), than in Passiflora. 

 It forms in Lavatera a dense zone that suggests a gathering of 

 nutritive material (deutoplasm). The fibrillEe are developed as a 

 felt around the nuclear membrane and enter the nuclear cavity 



