280 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



in any of these forms. Of Syringa, Juel (356) states that there 

 is quadripartition by cell-plates, but gives no figures to show it. 

 In the same way Duggar (14a) refers to Bignonia, but his figures 

 do not show cell-plates. 



In his paper on reduction in the pollen-mother-cells of dicoty- 

 ledons, Overton (51) presents a figure of Podophyllum, number 70, 

 which indicates cell-plate formation after the heterotypic division. 

 The mother- wall is not shown, and the division is not discussed 

 in the paper. Mottier (44a) in his paper on the same subject, 

 based also on Podophyllum, shows that cell-division does not always 

 occur after the heterotypic division. He gives two figures after 

 the homoeotypic karyokinesis with the four nuclei arranged in a 

 rhomb, with five spindles connecting them. No cell-plates are 

 shown. By four figures of late stages of the heterotypic division 

 he shows that the spindle fibers of that division disappear in the 

 center and arc replaced by a granular plate. In his text he says 

 only, "Die Zellplatte wird in der fiir Liliiim zuvor beschriebenen 

 Weise angelegt." We must conclude that in Podophyllum an 

 ephemeral cell-plate is formed after the heterotypic division, 

 but the division after the homoeotypic karyokinesis should be 

 further studied. 



Wille (81) in 1886 presented a paper on the formation of the 

 \vall of the pollen grains of 22 different plants, in which are inci- 

 dentally introduced a number of observations of interest in the 

 present study. He devotes especial attention to the thickening 

 of the mother-wall, which he contends is by intussusception, but 

 gives no evidence that anything more than a swelling or gelatiniza- 

 tion actually occurs. The thickened wall is said to be made 

 up of "wasserarme und wasserreichc Schichten," as Naegeli 

 and Strasburger held for starch grains. Though both mono- 

 cotyledons and dicotyledons were studied, he considers divi- 

 sion of the pollen-mother-cell as taking place in all cases by suc- 

 cessive bipartition by cell-plates. At the end of this paper Wille 

 reports a number of instances of the formation of pollen grains 

 in other than groups of four, the irregularities ranging from one 

 to fourteen in different species. He also described lobed micro- 

 spores as occurring along with the normal globular forms. 



It appears that in no instance is the evidence conclusive that 

 quadripartition of the pollcn-mothcr-cells of any dicotyledon is 



