Double Fertilisation in Angiospenns. 149 
Some further observations by Guignard 1 on Tulipa Celsiana 
and T. sylvestris revealed the fact that the various nuclei of the 
embryo-sac in these two plants were very irregularly arranged and 
more or less similar in appearance. The lower polar nucleus, which 
is morphologically different from the upper one, being often larger 
and with denser granulations, is situated at the base of the sac, 
below the antipodal nuclei. The antherozoids are elongated, but 
not spirally twisted, and are both equivalent. The oosphere is first 
fertilised. The second sperm-nucleus was seen fusing with the 
upper of the two polar-nuclei, hence union between these latter 
is a late occurrence in these plants. The second sperm-nucleus 
and the two polar nuclei fuse together as three distinct indivi¬ 
dualities, which gradually become less and less marked and 
finally vanish. He observed that at the moment of division of 
the fertilised ovum the sac contained four endosperm-nuclei. The 
phenomena above described hold good for the two species 
mentioned; but the different races of cultivated Tulips, on the 
contrary, agree in this respect with the Lily and Fritillaria. 
This author further observed 2 “ double fertilisation ” in several 
other orders of plants, such as Compositae, of which five or six 
genera were investigated, with the result that his obervations 
largely coincided with those of Nawaschin on Rudbeckia. In 
Ranunculaceae 3 the genera Caltha, Ranunculus , Helleborus, Anemone , 
Clematis and Nigella were examined. The two male-nuclei in these 
plants are spindle-shaped while within the pollen-tube, becoming 
elongated as they pass into the sac; they rapidly fuse with the two 
nuclei of the sac. In Nigella damascena the larger size of the male 
nucleus which fuses with secondary nucleus of the sac is correlated 
with the fact that the latter divides before the fertilised ovum. At 
the time of endosperm-formation the fusion of the male and female 
nuclei in the oosphere is not completed, and even after fifty 
endosperm-nuclei are formed in the sac the ovum remains still 
undivided. The same phenomenon was observed in Anemone 
nemorosa. Quite recently 4 the order Cruciferae revealed the same 
1 “ L’appareil sexual and la double fecondation daus les 
tulipes” (Aimales des sciences liaturelles, ser. 8, vol. xi., 
1900. 
2 “ Nouvelles reclierclies sur la double fecondation chez les 
vegetaux augiospermes ” (Comptes Rendus de l’Acad, des 
Sciences, vol. 131, 1900). 
3 “ J.a double fecondation chez les Renonculacees ” (Journal 
de Botanique, Dec. 1901). 
4 “ La double fecondation chez les Cruciferes’’ (Journal de 
Botanique, Nov. 1902). 
