^H 



FOURTH GROUP.SEED-PLANTS. 



raphe on the right and left of it. (Fig. 316 F, VI, VII.) When there is only 

 one integument present, which is usually strongly developed on the outer side, and 

 the nucellus is slender, consisting in many cases of only a central row of cells 

 and a layer of cells round it, the nucellus often has the appearance in the 

 middle stages of development of being a lateral secondary projection from beneath 

 the apex of the young conical funicle (Fig. 317 //). But the history of develop- 

 ment shows that here also the integument arises from beneath the nucellus, which 

 occupies the apex of the young ovule but is curved over at an early period by the 

 stronger growth of the protuberance on one side ; the same remark is true also of 

 ovules with two integuments, to which the former erroneous notion mentioned above 

 of the lateral origin of the nucellus was equally applied \ 



{ 



Fig. 317. Development of the anatropoiis ovule of Veybascuin pkoeniceum in axile longitudinal section. In / the 

 ovule is still a small conical body, the longitudinal axis of which is already curved by the stronger growth of the left 

 (convex) side. At y in No // is the rudiment of the (single) integument ; the rudiment of the nucellus arises at this spot 

 and apparently laterally on the young ovule. /// division of the mother-cell of the embryo-sac into three cells. IV an 

 older stage than No. //, the mother-cell of the embryo-sac not yet divided. A mother-cell of the embryo-sac (arche- 

 sporium), + the cell next it. After Warming. 



As regards position the ovules of Angiosperms may be grouped as follows : — 

 /. Ovules borne on the carpels, springing from the carpellary leaves ; these are 



1. Margmal, from the inflexed margins of the carpels (Figs. 302, 303, 



304, 307)- 



2. Superficial, growing from the inner surface of the inflexed halves of the 



carpellary leaves (Figs. 267, 299); in the genus Cabomba of the Nym- 

 phaeaceae any portion of the carpel, even the mid-rib, may produce ovules; 

 in Brascjiia, another genus of the same family, the o\'ules are all on the 

 mid-rib, and the same is the case in Asirocat'pus, a genus of the Resedaceae. 

 which has only one ovule ^. 



' The views which have been entertained with regard to the morphological value or dignity of 

 the ovule need not be noticed here, for their interest is now purely historical. The history of 

 development has shown that the ovule of the Angiosperms like that of the Gymnosperms is a 

 macrosporangium, which is distinguished from that of the Vascular Cryptogams only by the integu- 

 ments which spring from the rudimentary sporangium itself. The consideration of the malforma- 

 tions of ovules has generally caused confusion and prevented a true understanding of the matter. 



-' Eichler, Bliithendiagr. II. p. xvii. 



