206 SUBANTARCTIC ISLANDS OF NEW ZEALAND. [Ecological Botany. 



Another remarkable character is the presence of special extensive air-chambers 

 in certain species. Stilhocnrpa polaris, as I originally showed, possesses such chambers 

 (" Botanical Excursion," p. 261). Attached to the lower epidermis is a row of colour- 

 less, rounded, parenchymatous cells ; then comes a large air-chamber, equalling the 

 remaining chlorenchyma, which abuts on it above, and is made up of 4-6 rows of 

 palisade and 2-3 rows of pneumatic tissue, some of the cells of which jut into the air- 

 chamber. Somewhat similar structure occurs in Azorella Selago and Carex trifida, 

 and again, but more modified, in Luzula crinita, Scirpus aucklandicus, and Pleuro- 

 phi/llum speciosum. Schenck also shows the same structure to occur in Colobanthus 

 kergiielensis. 



Certain species exhibit the structure of aquatic plants such as seen in Brasenia 

 peltata — i.e., the interior and greater part of the leaf is made up of chains of cells 

 cutting off extensive air-spaces. Such structure is shown in Cotida lanata and Cotula 

 propinqua (plants of coastal rocks on peat or rock). Perhaps Myosotis capitata and 

 Ranunculus pinguis (plants frequently of wet peat) could be here included, though 

 both have a well-defined 3-layered palisade. Pringlea antiscorhutica, the well- 

 known Kerguelen cabbage, is also an excellent example of this type. 



The most marked xerophytic structure of the New Zealand subantarctic plants 

 is shown in the following : Colobanthus subulattis (small cushion plant of subalpine 

 rocks), thick unwrinkled cuticle, very thick-walled epidermal cells, chlorenchyma 

 of close cells, those near periphery elongated but central ones rounded ; Aciphylla 

 latifolia (tall herb exposed to wind), thick wrinkled cuticle, thick-walled epidermal 

 cells, strong development of stereome below epidermis and continuing through leaf 

 to the vascular bundles, stereome at margin of leaf, 4-layered palisade ; Aciphylla 

 antipoda (plant of similar station to last, but also in more exposed position on rocks 

 and debris), thick wrinkled cuticle, epidermis of thick-walled cells, stomata both 

 surfaces, stereome round periphery under epidermis, palisade dense but of similar 

 cells to the very open pneumatic tissue in centre of leaf. Olearia Lyallii (tree of 

 coastal forest), thick smooth cuticle of upper surface, thick-walled upper epidermal 

 cells, irregular lower epidermis of small thin-walled cells drawn out into mat of long 

 hairs protecting the many stomata ; Abrotanella rosvlaris (tiny rosette, rock-plant), 

 thick wrinkled cuticle, thick-walled epidermis, stomata slightly sunken, no cuticle 

 on under-surface, 3-4-layered palisade, dense pneumatic tissue of rounded cells ; 

 Phyllachne davigera (moderate-sized hard cushion plant of bogs and rocks), thick 

 wrinkled cuticle, stomata in all parts, closely packed chlorenchyma of round cells. 



The following are examples of plants with mesophytic structure : Ranunculus 

 subscaposus (plant of wet ground, near streams, in shade), no cuticle, 1-layered 

 palisade, shallow open pneumatic tissue ; Ranunculus aucklandicus (plant of wet 

 ground, near sea), almost similar to last, but with stomata on both surfaces) ; Acaena 

 Sanguisorbae var. antarctica (plant of meadows, coastal cliffs — almost everywhere, in 

 fact), no cuticle, 2-layered palisade, 2-layered pneumatic tissue ; Pratia arenaria 

 (plant of dunes, forest, meadow), thin-walled epidermis, no cuticle, stomata both 

 surfaces, 1-layered palisade, rather close, round-celled pneumatic tissue for greater 

 part of leaf ; Coprosma foetidissima (shrub of forest, scrub, and meadow floor), 

 very open pneumatic tissue. 



Certain peculiarities are exhibited by some of the species, Astelia suhulata 

 has a wedge-shaped (in section) mass of colourless water-tissue penetrating to centre 



