86 THE STRUCTURE OF FLOWERS. 



constriction indicating the union. The medullas, cortical 

 and epidermal layers, are also continuous throughout and 

 common to the whole. 



N^ow, the union of two opposite "appendages " to an axis, 

 as in the case of connate leaves, may take place. This may 

 be called foliar fasciation in which the fibro-vascular cords 

 of each " leaf " are embedded in a common parenchyma, and 

 all encased together within a common epidermis. 



If we regard the receptacular tube of, say, Fuchsia and 

 Narcissus in the same light, though adherent to the ovary 

 like a decurrent leaf of a thistle or Sedum, I see no argument 

 against the supposition that the tube, in such cases as these, 

 may be regarded as the fasciated petioles of the sepaline 

 and perianthial leaves, now adherent to the ovary within 

 them. 



A pear would seem to combine both axis and petioles, as 

 the base of the ovaries is situated much above the commence- 

 ment of the expansion of the pedicel (see Fig. 22, p. 90, 

 and Fig. 26, p. 94, and consult text). 



Each case must, however, be interpreted on its own 

 merits ; and I think there will be little difficulty about this, 

 if we recognize the fact that both the pedicel and floral 

 receptacle on the one hand, and the petioles or their floral 

 equivalents on the other, can alike assume all the features of 

 the so-called receptacular tube. 



Now let us apply these principles of union through 

 hypertrophy to flowers, and we have an interpretation 

 according to the theory advanced in this book : that differ- 

 ences of floral structure depend largely upon different dis- 

 tributions of nutrition in the several organs ; and that the 

 irritation set up by insects themselves is one of the most 

 potent causes of a flow of sap to certain definite places, 

 which encourages local growths, thereby inducing these 



