Reproduction of Angioiperres : Megnspore Stage. 



GYNOECIUM, similarly based on specialised leaves a 

 sporophylls. Thesebear megasporangia, commonly termed C 

 large spore is alone functional. Differentiation of an Ovary-chamber is the 

 character of the Angiosperm, as special adaptation for the protection of the < 

 from desiccation during their entire history to the stage of the Seed. Special 



I. Apooarpy : The typical carpel may be regarded as a 

 marginal ovules, and rarely with much of a sulk; the lamina being folded on 15 



upper surface to give an ovary-cavity; the margins rosed along a tutxrt, and the tip 

 elongated as styU, with a more or less closed stigma, as receptive surface, at the 

 extremity. Vascular supply to the ovules, originally one V.B. to each ovule; the 

 ovules many or few, ultimately one only as limiting case, and commonly found. 



The apocarpous gynoecium is the oldest and most elementary form of ovary- 

 construction : cf. Pea-Pod (Leguminosae), Ayw'Ugia, with many ovules ; C Urn ah* with 

 one only functional ; Ranunculus, one ovule only produced in each carpet 



II. Synoarpy : a more elaborate case, initiated by secondary growth-extension 

 intercalated below the original carpel-primordia ; the latter may be reduced, and soon 

 become more or less vestigial, as the ovuliferous function is passed on to the new 

 4 syncarpous ' zone ; remains of the original carpels may be traced in free styles 

 or stigmas; or the carpels may leave no trace beyond numerical suggestions, and the 

 stigmatic surfaces be of secondary nature ; e. g. ' commissural ', cf. Wallflower. 



In the simplest case the intercalated chamber is unilocular, and the ovules are 

 borne on the outer wall (case of ' parietal placentation ') ; the number of placentas 

 expressing the original carpel-number. 



A more complex case occurs commonly, giving ' axile-phcentation ', in which 

 pocket-depressions below the level of the floral apex, may be specialized as ovuliferous 

 regions ; the component loculi again presenting all phases of reduction to few, or 

 ultimately one ovule each. 



Both cases may co-exist, in greater or less degree, with a wide range of possftnV 

 ties, rendering generalizations under simple headings difficult, or even obscure; often 

 characteristic for large groups as ' families ' founded on such features. 



III. The Inferior Ovary : Previous examples assume the case of an ordinary 

 conical receptacle, as a ' condensed ' shoot-system, implying an axis with terminal 

 growing-point. The case of the crateriform apex involves further poasibiBtici, at 

 leading to more efficient protection and vascular supply of the ovary-chamber. In 

 all cases development is traced by reference to the apex of the floral axis. In the 

 inferior ovary the outer wall is receptacular in origin, and the ovuliferous region may 

 present parietal or axile placentation, or again any phase of reduction in ovule-content 

 A limiting case of two carpels in a syncarpous construction may be associated with 

 production of one basal ovule only (Compositae). 



Note: the object of such construction is (i) the maximum protection of the 

 ovules; (2) efficient vascular supply; (3) chance of cross-pollination indf Df ndcntly ; 

 (4) greater possibilities of special adaptation in fruit-stages, as also in dispersal- 

 mechanisms. Reduction-specialization in ovule-output, as conrroltng seed-output, is a 

 mark of higher organization. 



The Style includes any secondary intercalary extension of a carpel-tip, or distal end 



special cases, as a plumose tuft of ramuli giving increased area for collection of wind- 

 borne pollen ; or more extensive glandular regions, commonly papillose, and more 

 or less damp or viscid, for the adhesion of insect-borne pollen, thus rubbed off on the 

 brush-work of stigmatic papillae. The protection of such a damp surface of delicate 

 cell-units may be an essential factor in special cases of floral nvchantsm, and any 

 secretion must be regulated in osmotic value to that of the pollen-grains germinating 

 on it ; hence often a specific constant, and the chances of ' foreign pollen ' germinating 

 on any stigma may be remarkably small The elongation of the style is commonly 

 correlated with similar spacing-growth of stamen-filaments, or is utilized in the 



7 AS 



