farr: cytokinesis of pollen-mother-cells 271 



has observed quadrlpartltion. This includes three species of 

 Aloe, four of Iris, two of Sisyrinchium, three of Ixia, two of 

 Antholyza, and one each of Freesia, Haworthia, Monbretia, Gasteria, 

 and Apicra. He also refers to the literature on the occurrence of 

 quadripartition in monocotyledons and bipartition in the pollen- 

 mother-cells of dicotyledons. He cites as cases of the former the 

 work of Strasburger on two species of Asphodelus, and of Tangl, 

 Strasburger, and Juel on Hemerocallis, besides referring to his 

 own study of orchids, in all of which, except Cypripedium, he found 

 quadripartition. As presenting cases of bipartition in pollen- 

 formation of dicotyledons he mentions the following papers: 

 Strasburger on Ceratophylliim; Ernst and Schmidt on Rafflesia; 

 Strasburger, Frye, and Gager on Asclepias; and Frye and Blodgett 

 on Apocynum. As showing intermediate types of partition he refers 

 to the work of Samuelsson on Anona and Aristolochia, to his own 

 observations on Magnolia, and to those of Andrews on Magnolia 

 and Liriodendron. Guignard has not yet published his study of 

 the cytology of the process, but notes the tetrahedral arrangement 

 in Sisyrinchium, and the thickening on the inner surface of the 

 mother- wall at the point of insertion of the partition. The paper 

 very clearly establishes the situation as to quadripartition in the 

 flowering plants. 



Hofmeister (32&) in 1867 showed that division in the pollen- 

 mother-cells of Tradescantia occurs by cell-plate formation. And 

 Baranetsky (4) has since confirmed this. Miyake (42) shows a 

 figure (152) of what should probably be interpreted as a cell- 

 plate in this form; and the nuclei lie far apart at the time of 

 its formation. In Allium also he figures a cell-plate after 

 the heterotypic karyokinesis with the nuclei far apart. He also 

 reports a cell-plate following the same division in Galtonia. 

 Strasburger (67a) had previously shown that two successive bi- 

 partitions by cell-plates occur in Fritillaria, Lilium, Allium, and 

 Anthericum. His figure of the last-named form shows very well 

 the centrifugal splitting of the cell-plate and the centrifugal 

 formation of the new wall between the new plasma membranes. 

 In Allium he claims, as Wimmel (82) had previously figured, 

 that the mother-wall enlarges and that the cell-plate after the 

 heterotypic karyokinesis may be accompanied by a constriction, 

 "ein ringformiges Beginnen dieser Zellwand an der Wand der 



