526 PART III. THE CLASSIFICATION OF PLANTS. 



terminally at the apex of the floral axis (e.g. Polygonum, Piper, 

 Naias, Fig. 338 F); or laterally, below or behind the actual apex 

 (e.g. Composite, Fig. 338 D). 



For other descriptive terms relating to the ovule, refer back to 

 p. 437. 



The macrosporangium or ovule, consists primitively of a mass of 

 cellular tissue, the nucellus, invested by one or two integuments, 

 with a micropyle at the apex (see p. 436) : generally speaking, two 

 integuments are present in the Monocotyledons, in most polypetal- 

 ous Dicotyledons (with exceptions such as some Umbelliferae and 

 Ranunculacese), and in the Cucurbitaceae among Gamopetalae; 

 whereas there is only one integument in the Gamopetaloe (except 

 Cucurbitacea3) and in the polypetalous orders, Umbelliferae and 

 Ranunculaceae. In some few cases (e.g. Santalaceae, Loranthaceae, 

 Balanophoracese), 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. 438. 



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 staminodia (e.g. the posterior of the 

 five stamens in Gesneraceae ; a whorl in Parnassia ; one or more 

 whorls in various Lauraceae) : in some cases it is borne on the 

 carpels, in the septa of a multilocular ovary (septal glands of many 

 Monocotyledons, Liliacese, Amaryllidaceae, and Iridacea3). Generally 

 the nectary is borne on the floral axis, when it is described by the 

 general term disc : it may be a single tubular outgrowth (Crista- 

 tella) or a flattened scale (other Capparidacese, some Resedaceae) ; a 

 single posterior scale ; or several in a whorl, as scales or rounded 

 prominences (e.g. Apocynacese; two in a whorl in Vinca, Dipladenia; 

 five in Forsteronia; many in Nerium: CruciferaB, generally four: in 

 Vitis five) ; or as a ring of tissue, round the base of the ovary 

 (e.g. Rutaceae, Anacardiaceae, Rhamnaceae, Celastraceae) ; or on the 

 upper surface of the inferior ovary (e.g. Umbellif erae) . 



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

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



