230 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
is quite as great as that between many of the extinct species of 
Liriodendron. Of these, as many as fourteen have been described, besides 
varieties, the fossil remains or impressions being found in the Cretaceous 
and Tertiary strata. The author thinks it probable that the genus may 
have been derived from certain forms of Magnolia. 
Swollen Roots of Monocotyledons.* — M. L. Daniel discusses the 
structure and function of the napiform or dauciform roots or “pseudo- 
rhizes ” which occur abundantly in many bulbous Monocotyledons, 
especially Crocus and Gladiolus. He considers these to be not acci- 
dental, but normal, though transitory structures, formed for the purpose 
of storing up food-material, whenever from either external or internal 
causes the ordinary structures are unable to supply sufficient nutrition, 
as, e. g. during excessive dryness. They are either solitary or are formed 
in pairs or groups, and are abundantly provided with absorbing hairs, 
presenting, in their structure, a close approximation to that of true 
x’oots. In Gladiolus the transitory reserve-substance is glucose. 
0. Physiology. 
Cl) Reproduction and Embryology. 
Fertilization of the Casuarinese.t — From observations made by 
Dr. M. Treub on several species of Casuarina, especially C. suberosa, he 
arrives at the remarkable conclusion that the mode of fertilization differs 
essentially from that which takes place in the rest of Flowering Plants. 
The female flower is composed of two carpels ; there is a single small 
ovary, surmounted by a massive axial structure, corresponding to the 
style in other plants, and terminating in two stigmas. As soon as the 
ovarian cavity is formed it closes completely, and in it appear two 
parietal ovules, united by strings of cellulose to the base of the axial 
structure or summit of the ovarian cavity ; the pioint of adherence is 
called by M. Treub the bridge ; aud the ovule adheres to the ovarian 
cavity below by the funicle, above by the bridge. 
In the development of the ovule, certain large hypodermal cells, the 
archespore-cclls, at the summit of the nucellus, divide tangentially ; two of 
the cells produced on the inner side, the primordial mother-cells, divide 
further into a cylinder which occupies the centre of the nucellus, the 
sporogenous tissue, surrounded by flattened cells, the tapetal cells ; 
the cells of the sporogenous tissue correspond to the mother-cells of 
the embryo-sac of other Angiosperms. They divide transversely into 
large megaspores ; the small inactive cells usually become absorbed ; 
while in C. glauca and liumphiana tracheids are formed, possibly com- 
parable to the elaters in the Hepaticae. The megaspores, of which there 
are usually from sixteen to twenty, elongate towards the chalaza, and 
some of these penetrate between the elements of the vascular bundle of 
the funicle. 
Most of the megaspores which develope have at their extremity two 
or three naked sexual cells resulting from the division of a single cell ; 
usually there is one, and only one, megaspore in each nucellus which 
* Rev. Gc'n. de Bot. (Bonnier), iii. (1891) pp. 455-61. 
f Ann. Jard. Bot. Buitenzorg, x. (1891) pp. 145-231 (21 pis.). 
