Cross. — Observations on some New Zealand Halophytes. 571 



Mesophyll : On Il\e whole, there was less differentiation of the tissues. 

 [a.) Pahsadic parenchyma — 3 layers only, and, these arranged less regularly, 

 with greater intercellular spaces ; the chlorophyll grains were slightly more 

 numerous but not so large. (6.) Spongy parenchyma greatly developed, and 

 with somewhat elongated cells. 



5. Selliera radicans. 



The leaves (fig. 15, h) were compared wnth those on ascending branches 

 (fig. 15, a), and w^ere found to be but half their thickness, decrease in size 

 being due to decrease both in the number of layers of cells and in their size. 

 Towards the upper surface, instead of palisade cells there were 3-4 layers 

 of rounded rather closely packed cells, Avhile beneath there were 5-6 irregular 

 layers of somewhat larger rounded cells, with greater intercellular spaces. 

 The chlorophyll bodies were not more numerous, but somewhat larger. The 

 cuticle was much thinner. 



6. Cotula dioica. 



This species showed very little change, though the leaves were slightly 

 thinner. There was no decrease in the number of layers, though the cells 

 were in some cases somewhat shorter. 



7. Cotula coronopifolia. 

 Leaf (Fig. 16, h). 



Epidermis had somewhat thinner cuticle. 



The palisade parenchyma showed only two rows of closely packed cells,- 

 and in most cases the chlorophyll grains w-ere slightly larger, though not 

 more numerous. 



The spongy parenchyma was scarcely so w^ell developed, but had rather 

 more intercellular spaces. Probably in the typical halophytic form this 

 may be largely developed to form a water-bearing tissue. 



Not too much confidence is placed in these results, as the decrease in 

 thickness in so short a time seems too great to be accounted for by the 

 absence of salt in the soil only. Very probably it was to some extent due 

 to other external conditions, such as their being grown within doors and in 

 pots. Had this comparison been intended for the chief section of the work, 

 time would have been taken to repeat Lesage's classical experiment, and so 

 to confirm the above results. In any case, it must be assumed that the 

 absence of salt in the soil is the principal cause of the decrease in the thick- 

 ness of the leaves. Then, again, as Lesage found during his experiments, 

 this decrease is due to a lessening of the number of the pahsadic layers, or 

 to a diminution of the size of their cells, or to both. 



General Conclusions. 



In the first place, w^ith regard to the life form and external morphology 

 of these New Zealand halophytes, they exhibit, on the whole, the following 

 characteristics : — 



(1.) A tendency to adopt a prostrate habit {Atriplex, Selliera), and to 

 present a more or less stunted appearance {Plagianthus). Several explana- 

 tions have been put forward to account for this stunted condition. 



