Griffin. — Development of New Zealand Conifer Leaves. 57 



juvenile form, or the awl-shaped, which is the mature form, 

 the more primitive ? This is a question which needs careful 

 observation before it can be answered. It has generally been 

 thought that the flattened form is the more primitive, and that 

 the awl-shaped is the modified form. This is not the case ; the 

 flattened form is really the modified leaf, and the awl-shaped 

 the more primitive. By a very careful observation of the ex- 

 ternal form alone this conclusion would be arrived at, and it is 

 strengthened so as to leave no doubt at all by the study of the 

 anatomical structure. 



Let us first just look at the relative positions of the two 

 kinds of leaves on a plant. By a comparison of a number of 

 plants we arrive at this conclusion — i.e., the flattened form is 

 never found on main stems, but only on the lateral branches. 

 The rounder form occurs on both the main stem and on the 

 lateral branches at different periods of development. Again, 

 the flattened forms are not, as has been supposed, the first- 

 formed leaves on a germinating plant. If a seedling be carefully 

 examined during germination it will be seen that the awl-shaped 

 leaves are those which appear first on the main stem. One or 

 two of these leaves are also formed at the base of the branches 

 of the first whorl, but higher up we find only the flattened form. 

 This form is the only one found on the lateral branches in older 

 plants, with the exception of the prophylls, which soon die off. 

 When the plant has reached a certain stage, however, the awl- 

 shaped leaves too begin to appear on the lateral branches, and 

 the other form becomes rather smaller and not so flattened. 

 In the mature stage the awl-shaped leaf is the general rule on 

 both stem and branch, being finally triumphant. 



Now, the lateral branches are alone in a suitable position 

 for assimilation, and since they alone have flattened leaves, we 

 surely must conclude that these branches bear the modified 

 form so as to increase the surface for assimilation. This theory 

 is strengthened by the fact that all lateral branches tend to 

 stand out at right angles to the stem, and hence expose the 

 whole surface of the leaves to the sun. For confirmation of 

 the theory we shall have to compare the anatomical structure 

 of the two forms on the same plant. 



Leaves of Seedling Six Months Old. 

 Flattened Form. 

 The leaf is on first sight apparently a much reduced specimen, 

 similar in shape, in transverse section, to the preceding species ; 

 but the strange position of the vascular bundle strikes one at 

 once. This is nearer one margin than the other, and the resin- 

 canal is opposite the nearer margin. I will now give the struc- 



