Gkeensill. — Leaf-structure of Coprosma. 351 



no cuticle and with thin walls. The differentiation into 

 palisade and spongy parenchyma at this stage is scarcely 

 more than indicated in the chlorophyll tissue (ch.) by those 

 cells which will become palisade parenchyma being more 

 tightly packed and less rounded off. The layer beneath the 

 upper epidermis has no chlorophyll corpuscles, thus marking 

 the differentiation into a hypodermal layer. The two or three 

 layers surrounding the pit consist of smaller cells very tightly 

 packed. The cells lining the pit (p. ep.) are longer in shape 

 than those of the epidermis of both surfaces. Some are 

 almost papillose, though there are no hairs to be seen at 

 this stage. The mesophyll of the leaf contains very few 

 chlorophyll corpuscles, and there are numerous bundles of 

 crystals (?'.) contained in the individual cells. In this section 

 the nuclei (n.) of all the cells are shown. Close beside the pit 

 is seen the vascular bundle (v. b) of the midrib, with paren- 

 chymatous cells {par.) above and below. These parenchy- 

 matous cells also contain numerous raphides (r.). 



Fig. 7 : The main features are similar to those seen in 

 fig. 2. This section, however, is unstained. There is an 

 upper (ep.) and a lower (I. ep.) epidermis of tightly packed 

 cells, somewhat larger than those of Coprosma baueri, but 

 with no cuticle. The differentiation into palisade and spongy 

 parenchyma is indicated by those cells which ultimately form 

 the palisade tissue (p. p.) being narrower and less rounded 

 in form. There are few chlorophyll corpuscles present in the 

 mesophyll of the leaf, and they are much smaller than in the 

 mature leaf. Crystals (r.) are present here also. The dif- 

 ferentiation into a hypodermal layer is shown also in this 

 case by the absence of chlorophyll. The epidermis of the pit 

 is very similar to that of the lower surface. There is a tuft 

 of unicellular hairs (h.) in the pit. The two or three layers 

 around the pit are here also closely packed, and smaller than 

 the remaining cells of the leaf. They contain few or no 

 chlorophyll corpuscles, as was also the case in Coprosma 

 baueri ; and in the mature leaf will be the colourless layers 

 inside the pit epidermis. 



Nature of the Pits. 



Dr. A. N. Lundstrom examined these structures in many 

 different species of plants, and was the first who made 

 thorough investigations into their nature. A summary of his 

 report was published in the "Journal of the Royal Micro- 

 scopical Society" (1888). A paper was also written on the 

 subject of " domatia " by Mr. Alex. G. Hamilton, which was 

 published in a number of the "Proceedings of the Linnsean 

 Society of New South Wales " (1896). In the species he de- 

 scribed was included Coprosma lucida. Dr. Lundstrom re- 



