30 6 Notes . 
Wille 1 counted five, six, seven, and even fourteen microspores arising from a single 
mother-cell. 
Moreover, Wille offers an explanation of the manner in which these additional 
pollen-grains are formed. Thus he writes, ‘ In dem Falle, wo bei Fuchsia , sp., 7 
Zellen entstanden waren, konnte ich nicht daruber im Zweifel sein, dass dies daher 
kam, dass drei der Zellkerne der Tetrade noch sich einmal getheilt hatten, ehe 
die Cellulosequerwande ausgebildet waren, wahrend der Vierte ungetheilt blieb/ 
Where five or six microspores were produced he believed the explanation to be 
similar. In the case of the higher numbers (14) he was unable to follow the 
cell-divisions, and is uncertain whether the additional pollen-grains are due to 
secondary divisions of one pollen mother-cell alone, or whether they are to be 
derived from two or more primitive mother-cells (Urmutterzellen) which have not 
become separated from one another in the usual manner. 
I have frequently counted six, eight, and ten microspores lying within one 
mother-cell wall of this plant. 
A study of the nuclear divisions of the mother-cell has shown that the high 
number of pollen-grains produced is due to the occurrence of irregularities in the 
distribution of the chromosomes during the anaphase of division, quite comparable 
with those described by Juel in Hemerocallis fulva , and no facts have been found to 
support Wille’s explanation. 
The prophase of the first division appears to take place in quite the normal 
manner, but during the anaphase it is seen that the numerous, small chromosomes 
frequently move very unevenly towards the spindle poles, and some, either singly or 
in groups, lag behind the rest and often become entirely cut off from the two main 
chromosome groups. Usually these separated chromosomes give rise to distinct 
nuclei, which vary in size according to the number of chromosomes they receive. 
A few cases were, however, observed in which the scattered arrangement of the 
chromosomes appears to have been such, that separate nuclear walls were not formed 
round each chromosome or group of chromosomes, but one lobed nuclear wall was 
produced which enclosed all the scattered chromosomes within its embrace 1 2 . It also 
occasionally happens that the separated chromosomes fail to become organized into 
distinct nuclei with nuclear walls, and in that case they appear to degenerate in the 
cytoplasm without taking any further share in pollen development. These cases are, 
however, infrequent, and in the majority of instances each detached chromosome or 
chromosome-group gives rise to a separate nucleus. 
During the second meiotic division the small, as well as the large, nuclei undergo 
karyokinesis and produce a distinct spindle. 
Often only two chromosomes can be seen to occupy the equator of a miniature 
spindle, and in some cases I believe only a single chromosome was present. 
The second division of the mother-cell nucleus is much more regular than the 
first, and up to the present I have not found that any of the supernumerary nuclei 
originate at this stage. The nuclear divisions of the mother-cell which have been 
1 Ueber d. Entwickelungsgesch. d. Pollenkorner, &c., 1886, pp. 60-1. 
2 In some cases the lobed nuclei almost suggest the existence of amitotic divisions. After 
a careful comparison of all the preparations showing the phenomenon, I believe, however, that the 
interpretation given above is the correct one. . 
