Notes. 
34i 
NOTE ON THE NUCLEI OF SOME UNISEXUAL PLANTS.— In 1907-8, 
at the suggestion of Mr. Gregory, I examined the nuclei of some unisexual plants 
with the object of studying any differences which might be detected between the con- 
stituents of the nucleus in the two sexes. 
Hydrocharis Morsus-ranae, Bryonia dioica, Lychnis dioica , Mercurialis perennis , 
Sagittaria montevidensis, and Cucurbita Pepo were investigated. The nuclei of the 
male and female plants were in all cases apparently identical, in both the number and 
the characters of their chromosomes. 
Some further points of interest seem, however, worth recording. 
1. A paired arrangement of the constituents was obvious in the somatic nuclei 
of both sexes of all these plants. In Hydrocharis and Bryonia very convincing 
examples of double reticula were seen, while in Lychnis and Sagittaria the fully 
formed chromosomes were seen lying side by side in pairs. These observations 
extend the account already given of a double structure in the somatic nuclei of 
Funkia ovata and F. Sieboldiana } It is also worthy of note that while the material of 
Funkia was all preserved by one method, several different methods were used in the 
fixing of the above material. 
2. In Lychnis an irregular number of paired aggregations were found in the pro- 
phases of the heterotype division of the pollen mother-cells. In the early stages of 
synapsis there are usually six pairs of these aggregations, the number then according 
with that of the somatic chromosomes (twelve). 
3. In the rudimentary ovule of the male flower of Sagittaria , one of the hypo- 
dermal cells becomes differentiated from the rest, and its nucleus goes through all the 
stages of a normal heterotypic division. It develops^ no further, but later becomes 
surrounded by a thick wall. 
4. In Cucurbita two cells were seen in the same nucellus with nuclei in process 
of heterotypic division. 
5. In Lychnis the embryo sac shows no trace of polarity up to the stage at which 
it contains four nuclei. The final arrangement is quite normal. 
M. G. SYKES. 
Botany School, Cambridge. 1909. 
1 Sykes, M. G., ‘Nuclear division in Funkia ’ : Archiv fur Zellforschung, B. i, 1908, pp. 392-3, 
and ‘ Note on the number of somatic chromosomes in Funkia ibid. , p. 526. Double structures in the 
somatic nuclei have since been recorded by Overton in Thalictrum and Calycanthus. Overton, J. B. 
* On the organization of the nuclei in the pollen mother-cells of certain plants, with especial reference 
to the permanence of the chromosomes’ : Annals of Botany, Jan. 1909, p. 19. 
