Ch. Ill, 9] SPECIAL FI"^XTIOXS OF LEAVES 



73 



fFig. 44 1. The chlorophyll, of course, is all near the surface, 

 and wanting in the interior cells of the chlorench^-ma, which 

 increase in number and size, and present a translucent aspect 

 if water is stored, but are opaque if much food is present. 

 Sometimes the upper parts of the 

 leaves become true foliage while the 

 bases alone store food, in which case 

 these storage parts, after the foliage 

 has -withered away, form collectively a 

 typical BCLB, as in Hyacinth fFig. 45). 

 In related plants the speciaUzation 

 has gone further, making a ch^-ision 

 between foliage and storage leaves, in 

 which case the latter become exclu- 

 sively food-storing organs, as in the 

 bulb scales of Lihes (Fig. 46). 



Another form of food-storing leaves, 

 ser\-ing also in some cases as foliage 

 and in other cases not, are the cott- 



LEDOXS or "seed leaves" of embryo Fig. 4.5. — a Hyacinth 



„i 4. 1 ... , 1 r 11 1 -11 "^ bulb, in section. The 



plants, later to be fully described. ^^,^, „, 3t„,^gg l^^,.^3 



In many kinds of plants, some of are the bases of last 



ju 1 1 ■ i ■ ■ j: X year's foliage leaves, and 



the leaves deviate m minor features ^ fe replaced, as they 

 from the t\-pical conchtion, in which either, by the bases of 



,1 11 1 11 ^- 1 the new leaves surround- 



case they are called collectively i^g ^j,^ g^^.,, .j^^t,,, 



BRACTS. Commonest of all are the CFiomFigaher. Vegetable 



little pale scale-like bracts which stand 



under each flower in a cluster, where apparently they have 

 no function, but represent foliage leaves in an arrested or 

 rudimentary state of development ; for it is a constant struc- 

 tural peculiarity of the higher plants that flowers originate 

 in the axils of leaves, that is, in the upper angle between 

 leaf and stem. Likewise little scale-like bracts occur just 

 below the leaf-like branches of Asparagus and florists' 

 Smilax (page 195). In the Linden the bract is much larger 

 (Fig. 47), and attached thereto is the flower cluster which 



