570 



PHANEROGAMS. 



bottom of the flowers, as in Nicotiana and I.abiatae. Frequently, however, special 

 hollow receptacles are constructed for this purpose, as is especially the case with the 

 bag-like appendages of the perianth-leaves (Fig. 396), usually called Spurs. In 

 Viola only one of the perianth-leaves forms a hollow spur, into which the ap- 

 pendages of two stamens are prolonged and secrete the nectar. The cup-shaped 

 stalked petals of Hellcborus and the slipper-shaped petals of Nigella secrete at the 

 bottom of their cavity the nectar which gathers there. 



The Ovule (macrosporangium) of Angiosperms usually consists of a clearly 

 developed, sometimes even very long stalk or Funiculus (as in Opuniia and Plum- 

 bagineae) — which, however, is sometimes entirely wanting, as in Grasses — and one 

 or two integuments which enclose the nucellus. [The general rule is that the 

 ovules of the gamopetalous Dicotyledons have one integument, and that the ovules 

 of the apetalous and polypetalous Dicotyledons as also those of the Monocotyledons 

 have two integuments. Exceptions occur, however : thus, among gamopetalous 

 Dicotyledons the Primulaceae, Myrsineae, Plumbaginaceae, and Cucurbitacese have 

 two integuments ; and among apetalous and polypetalous Dicotyledons the following 



Fig. 396.— Flowers with spurred sepals (A) and petals {B, C) ; A Kiscutella htspida, B Epimediitm grandiflorur 



C AquiUiiia canadensis. 



have only one integument, the Loaseae, Pittosporeae, Umbelliferae, Callilriche, 

 Empetrum, Hippuris, and Escallonia (Warming).] A third envelope, the Aril, is 

 frequently formed subsequently (as in Myristica, Euonymus, Asphodelus lulea, Aloe 

 subluberculata, &c. When the ovule is the terminal structure of the floral axis, 

 and has a short funiculus, it is orthotropous, as in Piperaceae and Polygonacese ; 

 the campylotropous form, i.e. where the nucellus together with its integuments 

 is itself curved, is comparatively rare, but occurs in Grasses, Fluviales, Caryo- 

 phylleae, &c. The usual form of the ovule of Angiosperms is the anatropous ; 

 the nucellus together with its integuments is inverted, so that the micropyle faces 

 the point of origin of the funiculus from the placenta (hilum) (Figs. 382,^, 383); 

 in this case the funiculus runs up the side of the ovule, coalesces with it, and is 

 termed the Raphe. The micropyle is frequently, especially in Monocotyledons, 

 formed by the inner integument only of the nucellus; but sometimes, especially 

 among Dicotyledons, the outer integument grows also above the opening of the 

 inner one, and the channel of the micropyle is then formed at its outer part (the 

 Exosiome) by the outer, at its inner part (the Endoslome) by the inner integument. 



