PHYSIOLOGICAL BOTANY. 



299 



The tap-root, which otherwise is absent in all Monoco- 

 tyledons, is particularly remarkable. 



Observations de Ovulo et Embryonibus Cycadearum. 

 Auct. T. A. GUIL. MIQUEL. Ann. d. Sc. nat. 3 ser. 

 vol. iii, p. 193. The following periods of the develop- 

 ment of the ovule appear to be distinguishable : 1. Before 

 impregnation, the cellular tissue of the nucleus beneath 

 the amnios becomes completely absorbed, and leaves a 

 cavity upon which the amnios lies. On the other hand, 

 the cavity of the amnios becomes gradually filled with 

 cellular tissue beginning at the base. 2. This cavity of the 

 nucleus, which is filled with mucus, then forms a cellular 

 mass, which does not become connected with the walls of 

 the cavity, but is inclosed by a membrane ; this is con- 

 nected with the membrane of the amnios and forms the 

 albumen. The formation of the albumen does not depend 

 upon impregnation, for it occurs even in sterile seeds. 

 The formation of the narrower cavities in the amnios 

 does not appear to be dependent upon impregnation. 

 3. Whilst the peculiar cavities are being formed in the 

 amnios, and the embryoblastanon (of Hartig) is growing 

 downwards, the entire amnios, excepting its external 

 membrane, descends into the hollowed apex of the albu- 

 men which is in progress of formation, and is inclosed 

 by it, and the apex of the albumen is covered by the outer 

 open apex of the amnios, as with a cap. 4. The cellular 

 tissue of the amnios now becomes absorbed, soft ; the 

 sacs traversing the mucus remain and are covered by a 

 soft membrane with which they become coherent. 5. As 

 the embryo enlarges, the embryoblastanon which is re- 

 flected upwards becomes compressed, the mucous matter 

 surrounding the sacs dries, and the membrane covering it 

 disappears, so that when the seeds are ripe, the embryo- 

 blastanon, with the sacs, are found in the form of an amor- 

 phous mass, under the persistent membrane of the amnios, 

 at the point of the root which is forming. The author 

 then speaks of the anthers of the Cycadeae, and states 



