56 Transactions. 



stomata only on lower surface, and the same vascular bundle. 

 The advance is in the character of the chlorophyll parenchyma, 

 for here we find, in the middle, cells which on either side of the 

 bundle are well elongated towards the margins. They have pits 

 on their end walls, but the lignification is very slight. 



In the shrub stage the leaves were much longer, and green 

 in colour. Their structure is very similar to that of the pre- 

 ceding leaf. 



This species, then, is interesting, for to some extent it is an 

 intermediate form between the two preceding. 



Podocarpus dacrydioides (Kahikatea). 



We now come to a species whose foliage is very different 

 from that of the three forms already described. Kirk gives the 

 general appearance and height of kahikatea in his " Flora," 

 and in his description notes that the young plants are always 

 of a deep-bronze colour. This is not always the case ; young 

 plants growing in the shade of the bush are, as a rule, of a bright- 

 green colour. Those that grow in open, exposed places, how- 

 ever, tend to assume a dull-bronze colour. This is due to a 

 colouring substance in the epidermal cells, and is very probably 

 of a similar nature to that found in matai ; but I have not 

 investigated its nature in either of the species. Its object in 

 young plants is no doubt to protect them from excessive light. 

 Hence in these young plants we find developed a remarkably 

 high power of adaptability to environment, by which young 

 plants grown in the open can protect themselves from the effect 

 of a too-intense light. 



Which Form of Foliage is the more primitive? 



From the earliest stages there are two distinct forms of foliage, 

 both forms of which are greatly reduced. One form is flattened, 

 and in appearance is very like a very much reduced totara- 

 leaf ; these are arranged in rows along two sides of the lateral 

 branches. The other form is shorter, awl-shaped, and adpressed 

 in spiral arrangement to the stem. Both kinds of leaves vary 

 a good deal in size and exact shape throughout development. 

 In some cases we find gradual transitions from one form into 

 the other, but very often abrupt changes take place. 



In the three preceding species the leaves were all of the same 

 kind, and the development in each was a more or less obvious 

 adaptation to environment, the younger stages being the simplest, 

 and the development gradual. In the case, however, of a plant 

 with distinct dimorphic foliage the development is not so simple, 

 and we are confronted with the question, Which form is the 

 more primitive ? Is the flattened form, which Kirk says is the 



