470 PART IV. CLASSIFICATION. 



whereas there is only one integument in the Gamopetalse (except 

 Cucurbitacese) and in the polypetalous orders, Umbelliferae and 

 Ranunculacese. In some few cases (e.g. Santalaceae, Loranthacese), 

 where the development of the ovule is degraded in correlation with 

 the parasitic habit of the plants, the ovule has no integument. 



The Macrospore or Embryo-sac. The structure and development 

 of the macrospore are described on p. 400. 



Accessory Organs of the Flower. The most common of these is 

 the Nectary^ a glandular organ secreting odorous or sweet liquid, 

 and thus attracting insects. The nectary is sometimes borne on 

 some other organ which is not thereby materially modified (e.g. 

 petals of Ranunculus, stamen of Viola) ; or on a specially modified 

 perianth-leaf (e.g. petals of some Ranunculaceae, as Helleborus, 

 Eranthis, Delphinium), or on staminodes (e.g. a whorl in Parnassia) : 

 in some cases it is borne on the carpels, in the septa of a multi- 

 locular ovary (septal glands of many Monocotyledons, Liliacese, 

 Amaryllidaceae, and Iridacese). Generally the nectary is borne on 

 the floral axis, when it is described by the general term disc : in 

 the Cruciferse there is generally a whorl of four nectaries at the 

 insertion of the stamens ; or the disc may be developed as a ring 

 of tissue round the base of the ovary (e.g. Rutacese, Rhamnacese, 

 Celastracese) ; or on the upper surface of the inferior ovary (e.g. 

 Umbelliferse). 



The position of the axial nectaries or discs is various : in some 

 flowers it is extra-staminal, and then it is situated either between 

 the androecium and the corolla (e.g. Capparidacese, Sapindace?e, 

 Resedacese), or less commonly, between the corolla and the calyx 

 (e.g. some Apocynacese, such as Nerium) : in others it is intta- 

 staminal, that is, between the androecium and the gynseceum (as 

 in Rutacese, Rhamnacese, Celastracese, etc.). Again, the disc is 

 generally hypogynous, but sometimes epigynous (Umbelliferse). 



Generally speaking, when the nectaries, of whatever kind, are 

 towards the outside of the flower, the anthers are extrorse (e.g. 

 Ranunculaceae) ; and when towards the centre of the flower, the 

 anthers are introrse. 



The General Histology of the sporophyte is sufficiently treated 

 of in Part II., and in the general account of the Phanerogams 

 (p. 400). 



The Embryogeny of the sporophyte is considered on p. 401. 



The Gametophyte is considered on p. 405. 



Fertilisation. After reaching the stigma (see p. 409) the pollen- 



