3x 



Some workers on Pines have brought to their aid in this connection the 

 position and number of the oil canals (Engelmann), or the number of parts of the 

 vascular bundle (Coulter and Rose) ; such, however, cannot be used similarly in 

 the species of Callitris, but only as aids to systematic work in conjunction with 

 other features. 



VIII. MOVEMENT OF LEAVES. 



Some reference has already been made to this subject under Article V, 

 Foliation, and a theory advanced. 



No opportunity occurred of studying the movements of the leaves in nature, 

 or rather in the field, to verify our opinion, but indications would suggest that the 

 two ventral surfaces are protected by a closing of the decurrent channel, by 

 an expansion or contraction or coming together of the longitudinal edges of the 

 leaves. {Vide physiological significance of this movement of leaves under 

 Foliation.) 



By a closing of this entrance the stomata are protected from hght, hot 

 winds, rains, &c., so that no twisting is required as in the leaves of some species 

 of Picea and Pinus. 



The free ends evidently have the power of spreading or becoming appressed 

 according to weather conditions, vide also remarks under Araucaria Cunninghamii. 



IX. GENERAL REMARKS ON THE LEAF OILS. 



The chemical results for the leaf oils of the several species of Callitris re- 

 corded in this work are somewhat comprehensive, and the data given are 

 representative of the individual species. The full results will be found under 

 each species. 



The material was all distilled at the Museum, and in several instances 

 gathered over a great extent of territory, and during a period of several years. 

 Particularly was this the case with C glauca, because this tree is the common 

 species, and is the most extensively distributed. In a lesser degree accumulated 

 results have been obtained with C. calcarata, C. verrucu^u, C, arenosa, &c 



