16 Transactions. 



of Massart, which are supported by soil-analyses (1910, pp. 156-65). The 

 prostrate habit of certain shrubs of dime-hollows in the north of Auckland 

 may, in part, be similarly explained. 



Acid peat soils favour the cushion and other xeromorphic growth-forms, 

 though mesophytic forms may also occur.* 



Phyllachne clavigera F. Muell. (Stylid.), and doubtless its allies of similar 

 cushion-form, can be made of much looser growth by moist-air culture 

 (Cockayne 1909a, p. 201). 



The shoots of Cotula Haastii T. Kirk (Compos.), one part of a plant rooted 

 in deep soil, and another part on rotten rock or shallow soil, exhibit certain 

 striking differences. These are chiefly in degree of intensity of characters. 

 The portion in shallow soil has smaller leaves, stiffer stems, more glands, and 

 the leaf-segments closer. The leaves are of a darker green, and are marked 

 with brown on the lower half, whereas there is no trace of brown on the 

 deep-rooting portion. A dune form of Acaena microphylla Hook. f. behaves 

 similarly in my garden, the leaves of non-rooting shoots being much smaller 

 than those of rooted shoots and broadly margined with brown, the " normal " 

 leaves being lighter green and faintly brown at the apices of the teeth at 

 most. This presence or absence of a dark colouring-matter would appear 

 of small importance were it not that dark-coloured leaves are a rather 

 frequent characteristic of New Zealand plants. 



Plants exposed to drifting sand may develop an upward growth. Thus, 

 Poa caespitosa Forst. f., although a steppe tussock-grass, when growing 

 on drifting sand in Central Otago gets more or less a sand-binding form. 

 So, too, with Phormium tenax Forst. and Arundo conspicua Forst. f. on 

 coastal dunes, though both are commonly swamp-plants. 



Scirpus frondosus Banks & Sol., a sand -binding plant of the most 

 extreme type, is not only endemic, but belongs to an endemic subgenus 

 (Desmoschoenus). Not only has this plant attained its growth-form in an 

 isolated dune-area, but, as Mr. E. B. Oliver suggests in a letter to me, 

 possibly in actual competition with the Australian Spinifex hirsutus Labill. 



At one place in Puhipuhi Valley, Seaward Kaikoura Mountains, nearly 

 all the species, both indigenous and introduced, growing on cold, wet, lime- 

 stone soil exhibit marked variegation, but beyond this tdaphic influence 

 they are of the normal green. 



Highly manured soil, as is well known in cultivation, acts powerfully 

 upon plant-form. In nature the same occurs. Plants of Sicyos australis 

 Endl. growing on ground manured by Puffinus sphcnurus in the Kermadec 

 Islands frequently produce male flowers in which " the petals turn green, 

 and assume more or less the shape and character of foliage leaves " (Oliver, 

 R. B., 1910, p. 132). Certain species appear confined to soil of the above 

 character — e.g., Senecio antipodus T. Kirk, of Antipodes Island, and Cotula, 

 Feather stonri F. Muell.. of Chatham Island. 



(b.) Light. 



The bright light of dunes probably leads to the red- or orange-coloured 

 stems of the rush-like Leptocarpus simplex A. Rich (Restiac), which are 

 green in the shade, and as salt-swamp plants not nearly so brilliantly 

 coloured. It is a moot point how far the reddish, yellowish, or brownish 

 hue of certain true dune-plants may be considered fixed and hereditary 



* See on this head Bum*, 1911, pp. 121,124. Xerophytes are confined to certain 

 zones in the bogs studied, the largest bog-areas being hydrophytic or mesophytic. 



