24 FLOWER-LEAVLS. [chap. 



from their functions, are styled, collectively, Oi-gaiis oj 

 Niiiritiun. 



2. The four series of leaves of which the flower is com- 

 posed do not each fulfil the same part in the production of 

 the seed. The corolla and the stamens are deciduous. 

 They fall away, leaving the pistil to mature into fruit. But 

 they do not generally fall until after an important function 

 has been accomplished by the stamens, either of the same 

 flower, or of another Orange-flower. 



The two outer series of flower-leaves, the sepals and 

 petals, may be regarded simply as organs designed to protect 

 the smaller and delicate parts which they enclose during 

 their early development ; and perhaps, also, the colour and 

 greater size of the petals may serve to attract insects which, 

 we shall find, have an important work to perform, as aids in 

 securing the formation of good seed. Hence the calyx and 

 corolla are termed the envelopes of the flower. As both 

 calyx and corolla are present in the Orange-flower, the 

 envelope of the flower is double^ or in two series. Hence 

 the flower is termed dichlamydeoiis. 



3. The anthers we have observed are divided lengthwise 

 into two lobes, which lobes, after the expansion of the 

 flower, become fissured near their margins, so as to liberate 

 the grains of pollen which they contain. About the time 

 that the anthers open to discharge their pollen, we may 

 observe that the stigma is rough, with microscopic projecting 

 cells which, upon minute examination, we shall find to be 

 slightly moistened. Upon the stigma, after the flower has 

 been open for a few hours in fine weather, there may usually 

 be found a few grains of pollen, which have either reached 

 the stigma by direct contact of the anthers, or by means of 

 some insect visiting the flower in search of honey, and 

 which, unwitting;! V, cotveyed some of the pollen, acciden- 



