BY MARJORIE ISABEL COLF.TNS. 249 



wliich are almost invariably pear-shaped, raiilticelliilar bodies, in 

 Nvliich a peripheral palisade-layer secretes the miicila_<ie or i-esin, 

 are only functional in the bud, and fall off with the stipules. 

 Only in one case— that of Woi-mia Bvrhidyei (Dilleniacese)— does 

 Groom record an instance of the secretion being derived from 

 glandular hairs on the leaves themselves, but, of this, no descrip- 

 tion is given. Volkens(6), however, has described many plants 

 in which the secretion is not only derived from glandular haiis 

 on the leaves themselves, but is also produced for a long period 

 of time, sometimes till maturity of the leaf. It is to Volkens 

 that we owe what knowledge we have of "leaf-lacquering ' as a 

 xerophytic adaptation. 



In the present investigation, the development of the leaf is 

 traced from the earliest stages to the mature condition, with 

 special reference to the glandular covering in the juvenile state, 

 the function, and fate of its secretion. 



MOKPHOLOm OF THK ShOOT. 



A shoot of Srcevola crassifolia is characterised by the vertical 

 arrangement of the leaves, which is consistent from the leaves in 

 the bud to those farthest away from the growing apex. I he 

 leaves are all ovate, moi-e or less toothed, petiolate, the base 

 being closely applied to the stem on its upper side. The leaf- 

 teeth are more marked in the bud and young lea\'es than in the 

 mature leaves, in whicli they are often obliterated by secondary 

 increase in thickness. The terminal bud is small, and, durint/ 

 the growing season (August toC)ctober, the Spring months about 

 Adelaide) it is hidden by the rapidly expanding young leaves. 

 Later, when this activity ceases, the bud is hidden at the base 

 of the most distal leaf. The leaves in the bud are not folded 

 about one another; they are opposite and vertical, the morpho- 

 logical upper surface of one leaf being closely glued to the upper 

 surface of the next youngest leaf. 



The whole growing region of the shoot in S. crassifolia is 

 covered with a sticky secretion, which gradually dries up farther 

 away from the stem-apex. As the leaves become expanded from 

 the bud, they increase rapidly in surface-area, and later lose 



