The Genesis of the Male Nuclei in Lilium. 
BY 
E. J. WELSFORD, F.L.S., 
Assistant in the Department of Plant Physiology and Pathology , Imperial College of Science. 
With Plates XVI and XVII. 
PAPER was published in 1913 by Professor V. H. Blackman and the 
l \ author, giving an account of fertilization in Lilium auratum and 
Lilium Martagon - 1 As a good deal of material remained over from this 
investigation, it seemed worth while to add to it and to undertake a study 
of the development of the male nuclei. 
It is a pleasure to take this opportunity of most sincerely thanking 
Professor Blackman for his generosity in handing over the material to the 
author. 
The earliest stage examined was that in which the young pollen-grain 
of Lilium auratum contains a single nucleus, lying near the centre of the 
cell ; its protoplasm is finely vacuolate throughout. Preparatory to the first 
post-meiotic division, the nucleus moves to one side of the pollen-grain and 
enters upon a spireme phase. The various stages of division follow one 
another rapidly (PI. XVI, Figs. 1-3), and result in the formation of two similar 
nuclei which lie close to each other against the wall of the grain (Fig. 4). 
The innermost or tube nucleus now moves towards the centre of the cell, 
after which its membrane becomes more clearly defined and its outline is 
often seen to have become irregular, so much so that it is sometimes lobed, 
a condition, however, more commonly found after the nucleus has passed 
some little way down the pollen tube. Meanwhile the membrane of the 
generative nucleus has become clearly visible, and the cytoplasm im- 
mediately surrounding it is seen to be so dense as to form a differentiated 
area. The cytoplasm of the pollen-grain, at this time, is very vacuolate, the 
walls of the meshes appearing to be formed of densely granular protoplasm 
(Fig. 6). The preparations suggest that the dense appearance of the genera- 
tive protoplasm is due to the granular matter which is concentrated in this 
part of the grain, whilst the remainder becomes more vacuolate. At first it is 
1 Blackman and Welsford : Fertilization in Lilium. Ann. of Bot., vol. xxvii, 1913, p. 3. 
[Annals of Botany, Vol. XXVIII. No. CX. April, 1914.] 
