Notes . 
305 
THE SUPERNUMERARY POLLEN-GRAINS OF FUCHSIA.— In the great 
majority of Gymnosperms and Angiosperms four pollen-grains are produced from 
each pollen mother-cell. 
Exceptions to this rule are, however, not wanting, and Coulter and Chamberlain 1 
record (largely from Wille’s observations) no less than twenty-three species in which 
a greater or less number of pollen-grains than four have been seen to arise from one 
mother-cell. To this list other names might be added, but I will only mention here 
that of A es cuius Hippocastanum , in which I have several times observed six micro- 
spores lying within one mother-cell wall. The manner in which this deviation from 
the normal number of microspores is produced has only been investigated in a very 
few instances. Apart from certain hybrids, such as Syringa rolhomagensis (Juel 2 ) 
and Bryonia (Tischler 3 ), which form a rather special case, there are, so far as I am 
aware, only two forms in which the cytological processes underlying the production 
of an abnormal number of pollen-grains have been worked out. Thus in the Cype- 
raceae ( Heleocharis , Car ex acuta) the work of Elfving 4 , Wille 5 6 , Strasburger 7 , and 
Juel 8 has shown that, whilst the mother-cell nucleus divides twice in the usual way, 
three of the nuclei thus formed degenerate, and only one microspore (surrounded by 
the thickened mother-cell wall) is finally developed from the mother-cell. Again, in 
Hemerocallis fulva Strasburger 9 and Juel 10 have shown that, during the anaphase of 
the first and second divisions of the mother-cell nucleus, the chromosomes are often 
irregularly distributed upon the spindle so that some of them, either singly or in 
groups, do not reach the poles, but become separated from their fellows, and each 
such group may give rise to a distinct nucleus. Each nucleus thus formed usually 
% becomes the centre of a separate cell, so that a larger number .of daughter-cells than 
four is frequently produced from a single mother-cell. Fullmer 11 (like Tangl 12 at an 
earlier date) is inclined to attribute at least some of the supernumerary microspores of 
Hemerocallis to the subsequent division of one or more of the tetrad nuclei, but 
Juel 13 entirely repudiates this suggestion. I have recently examined the pollen 
development of the ordinary greenhouse Fuchsia 14 , and I can fully confirm previous 
writers with regard to the occurrence of supernumerary pollen-grains in this plant. 
As long ago as 1850 Wimmel 15 called attention to the irregularities in the number 
and size of the pollen-grains produced from the mother-cell of Fuchsia , and in 1886 
1 Morphology of the Angiosperms, 1903, p. 125. 
2 Pringsheim’s Jahrb. f. wiss. Bot., Bd. xxxv, 1900, p. 638. 
3 Berichte d. deutsch. Bot. Gesellsch., Bd. xxiv, 1906, p. 83. 
4 Jenaische Zeitschr. f. Naturwiss., Bd. xiii, 1879. 
5 Christiania Videnskabs-Selskabs Forhandlinger, 1882, No. 16. 
6 ‘ Ueber die Entwickelungsgeschichte der Pollenkorner der Angiospermen,’ &c., 1886, Chris- 
tiania, p. 43. 
7 ‘ Neue Untersuchungen iiber den Befruchtungsvorgang bei den Phanerogamen,’ &c. Jena, 
1884, p. 11. 8 Juel, 1 . c., p. 649. 
9 Archiv. f. Mikrosk. Anat., Bd. xxi, 1882, p. 497. 
10 Pringsh. Jahrb. f. wiss. Bot , Bd. xxx, 1897, pp. 205-6. 
11 Bot. Gazette, vol. xxviii, 1899, p. 81. 
12 Denkschr. d. Kais. Akad. d. Wiss., Bd. xlv. Wien, 1882, p. 73. 
13 Pringsh. Jahrb. f. wiss. Bot., Bd. xxxv, 1900, p. 646. 
14 The pollen development of several different species of Fuchsia will be described in the full 
paper. 
15 Bot. Zeit., Bd. viii, 1S50. 
