ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 65 



sae ; there is never any coalescence between two adjoining cells. In 

 all the Leguminosse the synergidfe and oosphere, the antipodal cells, 

 and the secondary nucleus of the embryo-sac, are formed in the well- 

 known mode. The antii^odals often disappear after impregnation, in 

 consequence of the resorption of the subjacent nucellar tissue. Their 

 function, which is still very doubtful, seems to terminate shortly after 

 their formation. In other orders of plants, on the contrary, they in- 

 crease considerably, even after impregnation. As in the majority of 

 Angiosperms, there are no anticlinals, the mother-cell of the embryo- 

 sac being the last of the row. 



The presence of two nuclei in one or more cells, as in Cercis, 

 does not furnish any real analogy with the special mother-cells of 

 pollen-grains, because their division-walls are never completely 

 resorbed. 



Antipodals with several nuclei occur in some Eanunculaceae, as 

 Clematis and Hepatica triloba. The cells are always three in number, 

 and are inserted at the base of the embryo-sac, to which they are 

 attached by a kind of pedicel. Each of them has a nucleus containing 

 at first a single nucleolus. Long before impregnation two nucleoli 

 appear (in the hepatica) isolated in the substance of the nucleus ; there 

 is an internal line of separation between them corresponding to a 

 slight depression on the surface, which gradually deepens, and finally 

 divides the mother-nucleus into two parts, in which the same pheno- 

 menon may then be repeated, though this is not usually the case. 

 The whole then presents the form of four segments, in which the 

 nucleoli multiply ; and the protoplasm itself may be divided into five, 

 six, or even eight rounded fragments. The nucleoli do not elongate 

 into an hour-glass form, nor does the substance of the nucleus present 

 any median constriction, as is generally the case in fragmentation ; 

 they are rather granulations of the nuclear protoplasm, which soon 

 attain a considerable size. Finally the mother-nucleus is filled with 

 granular nucleoli, and becomes enveloped in the protoplasm. 



There appears, therefore, to be a special process of fragmentation 

 in organs whose function is completed, and which may be regarded 

 either as an organic residuum or as a degraded prothallium. 



Polyembryony in Mimosese.* — According to L. Guignard, poly- 

 embryony is a not uncommon phenomenon in the Mimosese, especially 

 in Schranckia uncinata and Mimosa Denhartii, and is allied, in the 

 former case, with other abnormalities of structure. 



In >S^. uncinata the tigellum is furnished, towards its extremity, 

 with an appendage of variable form, lobed, and descending below the 

 cap which clothes the embryonal radicle. The internal structure of 

 this appendage presents several interesting peculiarities. In addition, 

 several embryos, formed, of an internal normal structural axis, and 

 furnished, or not, with this appendage, present three or even four 

 foliaceous cotyledons of equal length folded longitudinally in various 

 ways. When the number of cotyledons is three, they occupy the 

 angles of an equilateral triangle, and one of them is inserted at a 



* Bull. Soc. Bot. France, xxviii. (1881) pp. 177-9. 

 Ser. 2.— Vol. II. ™ 



