450 SUMMARY OF CURRENT RESEARCHES RELATING TO 



debated systematic position of the Nymjyhaeacese. He finds nothing un- 

 usual in the formation of the megaspore — the archesporium is a single 

 hypodermal cell, and the tapetal cells are irregularly formed. In one 

 case two functional megaspores were observed side by side. The em- 

 bryo-sac contains abundance of starch when in the two- and four-celled 

 stages. Tho antipodal cells are very small and disappear about the timo 

 of the conjugation of the polar nuclei. One of the synergids persists for 

 a very long time. Shortly after the conjugation of the polar nuclei and 

 fertilisation of the egg the endosperm nucleus divides and a very deli- 

 cate wall is formed across the sac similar to that described by Schaffner 

 for Sagittaria. The upper nucleus forms the endosperm at the upper 

 part of the sac ; the endosperm persists until the embryo is fully formed. 

 From the lower cell is formed a long tube which grows towards the 

 chalazal end of the ovule, forming a passage by the absorption of the 

 nucellus. The author compares this nutritive function of the lower part 

 of the embryo-sac with the presumed similar physiological significance 

 of the antipodal cells in those plants (e.g. Ranunculaceae, Sparganium, 

 kVc) in which they are prominent. The embryo is at first spherical and 

 later forms a single cotyledon which was not observed to bifurcate as 

 Lyon describes for Nelumbo. The suspensor is late in forming and ap- 

 parently without function. The formation of the plumule and primary 

 root agree with the processes described by Lyon for Nelumbo. The 

 embryo shows no marked resemblance in its development to any of the 

 monocotyledonous plants of the Helobieae series ; but the development 

 of the embryo-sac and the formation of tapetal cells and megaspores 

 are very similar to what obtains in Potamogeton and Naias, while the 

 formation of the wall across the sac recalls the same process in 

 Sagittaria. Hence the author agrees with Lyon in placing Nymphaea- 

 ceae in or near the series Helobieaa (Naiadales). 



Embryogeny of Araliaceae.*— L. Ducamp describes the formation 

 of the ovule and of the embryo-sac and the development of the embryo 

 in this family. Of the two ovules which begin to be formed in each 

 carpel, one, the ascending, becomes aborted, while an embryo-sac is pro- 

 duced only in the other, descending ovule. The embryo-sac is generally 

 the lowest of a row of three cells formed by transverse division of a spore- 

 mother-cell. Frequently four daughter-cells were formed by successive 

 transverse divisions of the mother-cell — this is regarded as a primitive 

 condition. 



The course of division in the embryo-sac follows the general 

 plan as described by Strasburger. The nucellus becomes absorbed 

 except beneath the embryo-sac, and the internal epidermis of the integu- 

 ment forms a digestive layer, the cells of which are cutinised on tbe 

 surface. The cells of the integument become disorganised, and finally 

 the epithelial layer disappears, its place being taken by the superficial 

 layer of endosperm which becomes differentiated as a digestive sac. The 

 seed-coat is a membranous layer formed from the persistent outer epi- 

 dermis of the integument, outside which the endocarp forms a layer of 

 sclerotic elements. 



In the formation of the embryo the initial cells of the central 



* Ann. Sci. Nat., ser. 8. xv. (1902) pp. 312-402 (8 pis.). 



