ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 65 



form the suspensor and the terminal one the embryo proper. Dermatogen 

 is cut off at the fourth division of the embryo -^the suspensor consists of 

 four rows of cells, the two basal rows of which are swollen and elongated. 

 The primary endosperm nucleus divides before the egg ; the subsequent 

 •divisions give rise to endosperm on each side of the egg and in the 

 outer parts of the embryo-sac ; these divisions may be simultaneous, or 

 represent all stages in different parts of the sac. Endosperm forms near 

 ihe embryo, but is soon absorbed. 



Embryogeny of the Alismaceae.* — R. Soueges publishes a short 

 note upon the embryogeny of the Alismaceae, dealing more especially 

 with the development of the apex of the stem of Sagittitrla sagittaefoUa. 

 The present work appears to show that the monocotyledonous condition 

 cannot be derived from the dicotyledonous condition, for the cotyledon 

 in the former originates in a different and much more extended pro- 

 embryonic region than in the latter. In the monocotyledons the two 

 upper cells of the tetrad give rise to the quadrants, and the eight coty- 

 ledonary octants ; the two cotyledons of the second group arise solely 

 from the four upper embryonic octants, which are identical with the 

 four upper cotyledonary octants of the monocotyledons. The author 

 regards these observations as supporting Worsdell's theory, that the 

 organization of the apex of the embryo, by a phenomenon of acceleration, 

 represents a very reduced image of the organization of the stem of the 

 adult plant. In the dicotyledons the arrangement of the cotyledons 

 around the embryonic axis recalls the general arrangement of the leaves 

 around the stem. In the monocotyledons the mode of growth is mono- 

 podic and is seen in the embryo, where the main axis aborts, giving rise 

 to a single terminal cotyledon, while a new axis develops laterally. 



Ovule in Apocynaceae and Asclepiadaceae-f — L. Guignard publishes 

 a short account of his studies of the development and structure of the 

 ovule in the Apocynacese and the Asclepiadacete. After describing the 

 work previously done and the indefinite results obtained in the examin- 

 ation of these two groups, the author gives an account of the ovule 

 based upon the examination of twenty species. In the Apocynacea; the 

 number of ovules is variable and the development is not always identical. 

 Each ovule arises as a hemispherical papilla which elongates more or less 

 until it is cylindrical in form, the apex being conical and directed 

 towards the top of the carpellary cavity. The primordial mother-cell of 

 the embryo-sac or archesporium is formed just below the epidermis of 

 the apex ; subsequent development is variable. In the greater number 

 of species the nucellus is represented by a minute protruberance, and 

 since the tegument develops early and rapidly, the nucellus is frequently 

 imperceptible. In some cases the archesporium is completely enveloped 

 in an epidermal layer, which is quite distinct from the tegument, and 

 the nucellus may be regarded as complete. In other cases the epidermis 

 gradually disappears towards the base of the archesporium, and in others 

 it is only represented by a few cells. Thus, in the Apocynaceae the 



* Comptes Eendus, clxv. (1917) pp. 1014-17. 

 t Comptes Rendus, clxv. (1917) pp. 981-87. 



March Wth, 1918 F 



