496 REV. GEORGE HEXSLOW ON A THEORETICAL 



As other instances of the so-called " pseudo-monocotyle- 

 donous " plants among dicotyledons, Mirbel mentions the 

 " bulbous fumitary," Bulbocapnos, Cyclamen, some species of 

 Cereus, and Gucirea trichilioides of the Order Meliacece. These 

 I have had no opportunity of examining. 



It must always be remembered that more than one cause may 

 produce the same or analogous effects in plants ; so that while 

 I attribute the total or partial arrest of one cotyledon to an 

 aquatic habit, a similar arrest may arise from atrophy in conse- 

 quence of the way in which the embryo is folded in tlie bud. 

 This, I think, is well seen in Abronia arenaria** An analogous 

 case of arrest occurs in the structure of the conduplicate leaf 

 of the lime, in which one side of the base can grow more 

 freely than the other on the expansion of the bud. The result 

 is that the adult leaf is oblique at the base. The same result 

 occurs in the elm. Sometimes the check to grow T th is carried 

 so far as to completely detach the small basal lobe as a distinct 

 leaflet. 



As another instance of degradation, Utriculctria may be men- 

 tioned. Hegelmaierf also describes the embryo of Erigenia 

 biilbosa, Nutt., an anomalous umbelliferous plant, which has its 

 embryo greatly reduced, scarcely amounting even to the pro- 

 embryonic condition. 



The most instructive instance, however, would seem to be that 

 of Carum Bulbocastanum % ; for if the reader will compare the 

 series of figures given by Hegelmaier of the development of the 

 embryo of Sparganium ramosum § with those by the same author 

 of this umbelliferous plant, which produces a monocotyledonous 

 embryo, it will be seen that there is no appreciable difference 

 between them. The various stages of development up to that of 

 a globular proembryo are identical. Then begins the asymme- 

 trical growth in both alike, by one cotyledon acquiring a more 

 vigorous development in an axial line, so that the now elliptical 

 form of the proembryo bulges a little at the base (I- Finally, the 



Figured by Sir J. Lubbock, ' On Seedlings/ vol. i. p. 31, fig. 64 

 t Vergl. Unters. Entw. dicot. Keime, p. 144, Taf. viii. figs. 1-2. 

 \ Op. cit. Taf. vii. figs. 28-41. 

 § Bot. Zeit 1874, Taf. 10. 

 | Cf. op. cit., e. g. fig. 38 of Carum with fig. 20 of Sparganium. 



