252 



LEAF-ANATOMY OF SC.F.VOLA CHASSIFOLIA, 



lowed by a median, vertical division in the head-cell (Text-fig. !/•), 

 or the latter division takes place before the formation of the 

 second stalk-cell (Text-fig. \,d). A third stalk-cell is now formed, 

 either preceded or followed by the ultimate divisions in the head, 

 ceils ( Text-fig. 1,/, y). 



a b 



Text-Hg.*2 : II, surt'aee-view of a mature ^laiid; l>, pait of section through 

 yount>; leaf, to show crowdinu' of niatuie glands, and oveilappinsj; of 

 shields: ( x -)8()). 



The head of the matuie gland forms a shield of eight cells, 

 only four of which are .seen in transverse section (Text-fig. 2, n). 

 The shield, which is ultimately reflexed at the sides, is borne 

 upon a stalk of three tiers of cells, the two lower tiers being 

 composed each of a single cell, while the upper is composed of 

 two cells, which grow out laterallv to support the head-cells 

 (Text-fig.2,6). 



The Nature of the Skcretion. 

 The secretion, which covers both upper and lower surfaces of 

 the leaf, is a yellowish, translucent, homogeneous substance, 

 which is soluble in alcohol. It is very sticky when fresh, and 

 gives the characteristic red colouration of resin when tested with 

 Alkanna root-extract. A test for mucilage, carried out with 

 corallin-soda, gives a negative result. The secretion reaches its 

 maximum thickness in the bud, every available space between 

 the young leaves being filled up. This fact, which is probably a 

 result of the continuous production of glands in the bud, indicates 



