SEED-PLANTS. 307 



their great physiological importance are not attached to any particular member of the 

 flower, for almost every single part of it may serve as a nectary ; this fact is highly 

 characteristic of the relation between morphology and physiology, and the word 

 nectary expresses not a morphological but a purely physiological conception. The 

 nectary is often only a small spot at the base of the carpels, as in Nicotiana, or of 

 the stamens, as in Rheum, or of the leaves of the perianth, as in Fritillaria, which 

 forms the nectar without assuming a more distinct form ; sometimes it is a glandular 

 protuberance on the floral axis between the insertions of ,the stamens and perianth- 

 leaves, as in the Cruciferae and Fumariaceae ; some member, as a floral leaf, is often 

 changed into a hollow receptacle for secreting and preserving the nectar, such as the 

 hollow spur in Viola, or all the leaves of the inner floral envelope may form hollow 

 pitcher-like nectaries, as in Helleborus, or some may assume the strangest forms, 

 as the petals of Aconitum. 



Pollination is often followed, even before fertilisation, by striking changes in the 

 parts of the flower, especially in the gynaeceum, and most frequently when the parts 

 concerned are of a delicate character ; thus the stigmas, styles and petals wither, while 

 the ovary enlarges, as in Gagea, Ptischkinia, and other species ; the most striking result 

 of pollination is seen in many Orchidaceae, where the ovules are not formed till after 

 it has taken place. 



But changes still more energetic and varied are produced when the pollen-tube 

 reaches the embryo-sac, that is, by fertilisation; the oospore developes into the embryo; 

 the endosperm, already formed in the Gymnosperms and constituting the prothallium, 

 now begins to be formed in the Angiosperms ; the ovules with the ovaries increase in 

 size, and their tissues are differentiated and become lignified, or pulpy, or dry, etc. ; the 

 enlargement of the ovary which is often enormous, in Cocos, Cucurbita and other plants 

 several thousand times in volume, is a striking proof that the consequences of fertilisa- 

 tion extend to the rest of the plant in so far as it supplies nutrient material. Great 

 changes in form, structure and size take place after fertilisation as a rule only in the 

 carpels, placentas and seeds, but they occur sometimes in other parts as well ; for 

 example, it is the torus which forms the swollen pulpy mass which is known as the 

 strawberry, and which has on its surface the small and true fruits ; in the mulberry it 

 is the perianth-leaves which swell up and form the juicy envelopes of the fruit ; in Taxus 

 it is a cup-shaped outgrowth from the axis 'beneath the ovule which surrounds the naked 

 seed with a red fleshy envelope (the aril). Popular usage includes all parts, which 

 experience a striking change in consequence of fertilisation, under the name of fruity 

 especially when they separate as a whole from the parent plant ; the strawberry, and 

 the yew with its aril, the fig and the mulberry are all alike fruit. But botanical 

 phraseology confines the notion expressed by the word fruit within narrower limits, 

 though these are not very sharply defined. In as strict accordance as possible with 

 botanical usage the whole of the gynaeceum which ripens in consequence of fertilisation 

 may be termed the fruit ; if the gynaeceum consists of coherent carpels or an inferior 

 ovary, it produces a single entire fruit ; if the carpels are distinct, they each form a 

 mericarp or fruitlet ; at the same time this limitation of the conception is often incon- 

 venient, and it would seem to be better to define it differently in different sections of 

 the system. 



It must be borne in mind that the fruit taken morphologically*is not any new thing 

 on the plant ; all parts of the fruit that can be determined morphologically were formed 

 and so determined before fertilisation ; the change caused by fertilisation in the parts 

 of the gynaeceum is purely physiological. It is only in the ovule that anything mor- 

 phologically new is produced, namely, the endosperm and the embryo. 



Inflorescence. If a shoot which has hitherto produced numerous foliage-leaves, and 

 especially a strong primary shoot, ends in a flower, the flower is said to be terminal '; 

 but if a lateral shoot at once developes a flower, forming one or a few bracteoles at 

 most beneath it, the flower is said to be lateral. Sometimes the primary axis produced 



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