326 SUMMARY OF CURRENT RESEARCHES RELATING TO 



cular bundles, in Smyrnium, Pastinaca, Astrantia, HeracUum, and other 

 genera, comes to the conclusion that the gyncecium, although consist- 

 ing only of two carpels, represents theoretically two complete whorls, and 

 the ovary proper is represented by the stylopod and not by the cavity 

 beneath. The commissural bundle is formed by the union of four 

 placental bundles, and at maturity forms the podocarp. The separation 

 of the ripe carpels is determined by the lignification of the commissural 

 bundle, the drying and separation of the parenchyma forming the median 

 diaphragm, and by the breaking of the lateral vascular bundles at the 

 base of the fruit. 



Anatomy of Seeds of Acanthaceae.* — E. Schaffnit has studied the 

 structure of the seeds of Acanthaceae in a large and representative 

 number of genera and species. The seeds are almost always more or 

 less flattened, and curved inwards at the organic base. Exceptions to 

 this are those of Thunbergia, hemispherical and hollowed out on the 

 inner face, where they are inserted upon a cupular expansion of the 

 placenta ; also those of Elytraria {Tubiflora), which are almost spheroidal. 

 The size varies much ; of those measured by the author the largest, 

 Acanthus, has a length of 10-12 mm., the smallest, Hygrophila, measur- 

 ing only 0*5— 3*2 mm. The surface is smooth or provided with ridges, 

 scales, or warty excrescences, or with longer or shorter hairs. Endosperm 

 is present, but usually in such small quantities that the seeds pass with 

 systematists as " exalbuminous." Although the systematist errs techni- 

 cally here, his statement is physiologically correct, since the reserve 

 materials stored in this rudimentary endosperm would seem not to be 

 made use of in germination. In both endosperm and embryo the carbo- 

 hydrate constituent is not starch, but fatty oil, except in the case of 

 Acanthus, where starch is found. 



The author has examined a number of seeds of examples from all 

 the five recognised tribes of the order. Four types of surface are dis- 

 tinguished : — (1) Surface occupied entirely or partially by slime-hairs 

 or slime-cells. (2) Surface occupied entirely or partially by hairs not 

 becoming slimy on contact with water. (3) Surface uneven owing to 

 the presence of groups of epidermal cells which project beyond their 

 fellows. (4) Surface occupied by cells of uniform height, and conse- 

 quently smooth. 



A full account follows of each seed examined. Except for typical 

 cases which are dwelt on in detail, the method is that of the systematist 

 marshalling the data for his description. The size of the seed, the 

 clothing of its epidermis if any, the nature and contents of the tissues 

 of the testa and then those of the endosperm are succinctly dwelt with, 

 and, finally, the contents of the cells of the embryo. Except in the case 

 of Acanthus, where starch is the reserve carbohydrate, the cells of the 

 embryo were found to contain polyhedral aleurone grains and fatty oil, 

 to which were often added crystals of calcium oxalate, and rarely tannin. 



Nutrition of Plants in absence of Carbon dioxide.t— M. Molliard 

 has investigated the structure of plants grown in light without C0 2 and 



* Beih. Bot. Centralbl., xix.. Sect. 1 (1906) pp. 453-521 (18 figs, in text). 

 t Comptes Rendus, cxlii. (1906) pp. 49-52. 



