430 



PHANEROGAMS. 



place its body in certain definite positions by which it at one time brushes the pollen 

 out of the anthers, at another time attaches it to the stigma of another flower. The 

 diversity in the forms of flowers depends especially on these relationships, a com- 

 paratively simple plan of structure lying at the base of them all. The organs which 

 secrete the nectar, the Nectaries, are therefore of extreme importance in the life-history 

 of most Phanerogams; they are, nevertheless, usually very inconspicuous, and, — which 

 is very significant with respect to the relationship of morphology with physiology, — not- 

 withstanding their enormous physiological importance, they are attached to no definite 

 part of the flower in a morphological sense ; almost every part is able to perform the 

 function of a nectary. This term therefore does not denote a morphological but a 

 purely physiological idea. The nectary is usually only a small spot at the base of the 

 carpels (as in Nicotiana), or of the stamens (as in Rheum), or of the petals (^e.g. Fritil- 

 laria) which, without becoming more prominent, produces the nectar ; but frequently it 

 is in the form of glandular protuberances of the floral axis between the insertion of the 

 stamens and petals (as in Gruciferae and Fumariaceae). A particular organ, e.g. a petal, 

 is often transformed, for the purpose of secreting and storing up the nectar, into a 

 hollow receptacle, forming a spur-like protuberance [e. g. ViolaJ ; or all the perianth- 

 leaves become developed into hollow^ or pitcher-like nectaries (as in Helleborus), or 

 they assume the most w^onderful forms, like the petals of Aconitum. 



Even before fertilisation, pollination is usually followed by striking changes m the 

 parts of the flow^er, particularly in the gynseceum, and especially when the parts con- 

 cerned are delicate ; thus the stigmas, style, and corolla wdther, the ovary swells up (as in 

 Gagea and Puschkinia), and the like. The most striking result of pollination is shown 

 in many Orchideae, where the ovules are only formed as a consequence of this process. 



Those changes however which are excited by the entrance of the pollen-tube into 

 the embryo-sac, in other words by Fertilisation, are still more energetic and varied ; the 

 embryonic vesicle developes into the embryo ; the endosperm— formed previously in 

 Gymnosperms— originates in Angiosperms only subsequently to fertilisation; the ovules 

 grow along with the ovary, their layers of tissue are diiTerentiated, become lignified, 

 pulpy, dry, &c. The increase in size of the ovary, w^hich is frequently enormous (in 

 Cucurbita, Cocos, «&c., several thousand times in volume), shows in a striking manner 

 that the results of fertilisation extend to the rest of the plant, in so far as it aff'ords the 

 materials of nourishment. Striking changes in form, structure, and size take place after 

 fertilisation, especially in the carpels, placentae, and seeds ; but very frequently similar 

 changes result also in other parts. Thus, e.g., it is the receptacle that constitutes 

 the fleshy swelling which is called the strawberry, on the surface of which are seated 

 the small true fruits ; in the mulberry it is the perianth of the flowers that swells up 

 to form the succulent coating of the fruit ; in Taxus it is a cup-shaped outgrowth of 

 the axis beneath the ovule (the aril) that surrounds the naked seed with a red fleshy 

 coating, &c. Popular usage includes under the term Fruit all those parts which ex- 

 hibit a striking change as the result of fertilisation, especially when they separate as a 

 whole from the rest of the plant ; in ordinary language the strawberry, as well as the 

 seed of the yew surrounded by its aril, the fig, and the mulberry, are all fruits. Botanical 

 terminology limits the idea of Fruit within narrower boundaries, which, however, are 

 not yet sharply defined. In the most exact use of botanical terms, the whole of the 

 gynaeceum which ripens in consequence of fertilisation may be termed the Fruit. When 

 the gynaeceum consists of coherent carpels or of an inferior ovary, the flower produces 

 a single entire fruit ; if the carpels do not cohere, each forms a part of the fruit, or a 

 fruitlet. This limitation of the term is often, however, inconvenient ; and it would 

 seem preferable to give it a definition which will vary in the diff'erent sections. 



The point to be most clearly borne in mind by the student is that the fruit is 

 not a new plant-structure. All the parts of the fruit which are morphologically de- 

 terminable originate and assume their morphological character before fertilisation ; 

 the result of fertilisation is merely a physiological change in the parts. The only new 



