Feb., 1904.] 



Nymphaeacae and Helobiae. 



87 



19). There is the same opening on one side, and on the back a 

 connection of the two lobes, only to a less extent. Unless special 

 care were taken in reconstructing such an embr}© from serial sec- 

 tions, one might readily take it for a Dicotyl. It will be evident, 

 however, from a comparison of the figures that the Castalia 

 embrj'o represents only the extreme of the lobing shown in 

 Nelumbo and Njniiphaea. 



There is a structure present in various Helobiae which deserves 

 special attention in discussions on the relationship of the Nym- 

 phaeaceae. The so-called macropodous embryos of Halophila, 

 Ruppia, Zostera and other genera appear to the writer to throw 

 considerable light on the peculiar structure of the Nymphaea 

 embr3-o. The enormous development of the basal or hypocotjde- 

 donary region of the embrj-o in such widel}' separated genera 

 shows a strong and peculiar tendency in the group of Helobiae. 

 In such typical forms as Sagittaria latifolia, Zannichellia palustris 



Fig. I. vSimilar parts are indicated as follows : c, cotyledon, and li, the 



basal or lateral region developed into an expanded organ in some enibr3'os. 



a— Embryo of .Sagittaria latifolia. b— Embryo of Zannichellia palustris. c— Embryo 

 of Vallisneria spiralis, d - L,ongitudinal half of embryo of Ilalophilia ovalis, after Balfour, 

 e -Section of ^-oung embryo of Erythronium americanuni showing beginning of massive 

 development of basal region, f — P^mbryo of Ruppia rostellata, after Wille. g — Longitudi- 

 nal half of embryo of Zostera maritinia, after Rosenberg, h —Young embryo of Nelumbo 

 lutea, after Lyon, i — Older embryo of Nt-lumbo Uitea, after Lyon. 



and Vallisneria spiralis (Text Fig. i, a, b, c) there is barely a 

 hint of such a development. In some other Monocotyls, as, for 

 instance, in Erythronium americanuni, the basal region of tlie 

 embryo early shows a rapid development, growing into a massive, 

 lobed structure which functions as an absorbing organ ( Text Fig. 

 I, e), This is no doubt the purpose of the massive expansions 

 and lobes present in Halophila, Ruppia, Zostera, Nelumbo, Nym- 

 phaea and Castalia (Text Fig. i, d, f, g, h, i, and Figs. 14-19). 

 To the writer there is no more reason for calling the ridge or 

 lobes of the Nj-mphaeaceae, cotyledons, than the remarkable 

 expansion at the base of the embryo of Zostera. The basal 

 expansion in the Castalia embryo, to the writer, cannot represent 

 the same or homologous structure as the cotyledons of Sagittaria 

 or Bursa. According to this view the so-called cotyledons of 

 Nelumbo, Nymphaea and Castalia represent hypocotyledonary 



