Studies in Spore Development. 
II. On the Structure and Division of the Nuclei in the 
Compositae . 1 
BY 
RUDOLF BEER, B.Sc., F.L.S. 
With Plates LXVI and LXVII. 
I N 1900 Merrell (16) published an account of the life-history of SilphiUm y 
in the course of which some reference is made to the nuclear phenomena, 
both in connexion with the development of the embryo-sac and with that of 
the pollen-grains. He found that eight is the reduced number of the 
chromosomes in this plant. 
In 1905 Juel (13) added materially to our knowledge of the nuclear 
divisions taking place in the Compositae by his studies of Taraxacum , 
Hieracium umbellatum , and Crepis tectorum. In the last-named species he 
found the reduced number of chromosomes to be only four. 
Previous to this work, Juel had published (12) an interesting account of 
his investigation of Antennaria dioica and A. alpina , in which the mitotic 
phenomena were also noticed. The most comprehensive work, however, 
which has recently been published upon the nuclear phenomena of the 
Compositae is that which has been carried out by Rosenberg (19 and 20) 
and Lundegardh (15). 
A number of species were examined in these investigations, 2 with the 
result that they were believed to afford strong evidence in favour of the 
existence of prochromosomes in these plants and to furnish striking ex- 
amples of the parasynaptic origin of the chromosomes. A condition 
resembling that of the second contraction described by Farmer and Moore 
(5) was recorded by both Rosenberg and Lundegardh in several species of 
Compositae, but they regard it merely as a chance arrangement of the 
nuclear contents without any essential significance in the development of 
the heterotype chromosomes. 
1 I am indebted to the Government Grant Committee of the Royal Society for the loan of 
a Zeiss 2 mm. apochromatic objective (1-40 aperture) used during the research. 
2 Hieracium venosum, H. Auricula, Tanacetum vulgare, Crepis virens , Calendula officinalis , 
Achillea millefolium, Anthemis tinctoria, and Matricaria Chamomilla. 
[Annals of Botany, Vol. XXVI. No. CXII. July, 1912.] 
3 A 
