270 'MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



Of cell-division in the pollen-mother-cells of the higher plants 

 von Alohl (43c) as early as 1851 made the following remark: "Eine 

 eigenthiimliche Bildungsweise, welche die Theilung der Zellen 

 und die freie Zellhildung verbindet, zeigen die Pollenkorner und 

 die Sporen der hoheren Kryptogamen. Die Mutterzelle der- 

 selben theilt sich nach vorausgegangener Entwickelung von \ier, 

 aus der Theilung eines einzigen Kernes hervorgehenden Zellen- 

 kernen und gleichzeitiger Resorption desjenigen Kernes, welcher 

 zu ihrer Entstehung Veranlassung gegeben hat, durch Einfaltung 

 ihres Primordialschlauches und allmahlige Ausbildung von Scheide- 

 wanden (derenesjenach der relativen Lage derZellenkernevieroder 

 sechs sind) in vier Abtheilungen (Naegeli's Specialmutterzellen) 

 oder sie theilt sich zuerst in zwei Abtheilungen, welche sich wieder 

 in je zwei Kammern (Naegeli's Specialmutterzellen zwei ten 

 Grades) abtheilen. Hofmeister (32a) in 1861 attempted to 

 distinguish between the monocotyledons and dicotyledons on the 

 ground that the cell-plate in the former is progressively formed 

 from one side of the cell to the other, whereas in the latter, ac- 

 cording to von Mohl's observations on the Malvaceae, it develops 

 centripetally. At the same time he reported that quadripartition 

 occurred in Naias major and in two species of Iris. Later (326) 

 he placed pollen-mother-cells of Iris in water and found that in 

 one-half hour the mother-wall becomes thickened and the proto- 

 plast divides by constriction furrows. Dippel in 1869 distin- 

 guished between the monocotyledons and dicotyledons on the 

 basis of bipartition and quadripartition in the pollen-mother-cells 

 respectively; and Samuelson (60) and others have more recently 

 reiterated this \'iew, noting such exceptions as Nymphaea and 

 Asclepias. 



Guignard has been most active in accumulating evidence that 

 quadripartition occurs in monocotyledons. He first found it in 

 orchids (26a) where cell-plates are formed from a series of granules, 

 and stain a pale violet with haematoxylin. He shows only one 

 figure of the process, and in this the four nuclei lie in one plane 

 and granules but no plates are present in the equators. On the 

 other hand, Hofmeister's (3 2a) figures of bipartition in Neottia 

 ovata and Orchis Morio indicate incipient constriction, but are 

 unaccompanied by descrii)tion. Guignard (26c) very recently 

 has published a note giving a list of monocotyledons in which he 



