6 Transactions. 



the case may be. And perhaps it is allowable to go further, and say that 

 if several allied plants grow in close proximity in sufficient numbers, and 

 preserve their distinguishing characters, they are probably distinct, and 

 would come true from seed. A case of this latter class is to be seen at 

 the lower gorge of the River Waimakariri, Canterbury Plain, where the 

 vars. microphylla Hook. f. and prostrata T. Kirk of Sophora tctraptera J. Mill. 

 grow side by side, and in this case I have proved experimentally that both 

 varieties come true from seed. So, too, with certain forms of Acaena 

 Sanguisorbae Vahl. growing on subalpine fell-fields. 



There is no need to multiply instances such as the above ; suffice it to 

 say that both from experiment and ecological observations I am satisfied 

 that elementary species are very numerous in the New Zealand flora, especially 

 in certain genera — e.g., Calamagrostis, Danthonia, Poa, Festuca, Scirpus. 

 Uncinia, Car ex, Luzula, ? Phormium, Ranunculus, Cardamine, Pittosporum, 

 Eubus, Acaena, Carmichaelia, Oxalis, Coriaria, Aristotelia, Pimelea, Epi- 

 lobium, Leptospermum, Anisotome, Aciphylla, Gaultheria, Dracophylhtm. 

 Gentiana, Myosotis, Veronica, Coprosma, Celmisia, Cotula, Craspedia, and 

 Senecio. On the other hand, many species vary to a slight degree only. 

 and are to be recognized at a glance. 



III. Variation. 



Apart from constant hereditary distinctions, there are " the individual 

 differences," as Darwin called them (1899, p. 31), or " fluctuating varia- 

 tions," as they are now frequently designated. These are supposed to 

 depend upon a reaction of the organism to a change of environment. 

 Klebs (1910, p. 235) distinguishes two kinds, the one " caused by different 

 external conditions during the production either of sexual cells or vegetative 

 primordia," and the other " is the result of varying external conditions 

 during the development of the embryo into an adult plant." The two sets 

 of influences cannot as yet be sharply differentiated. The following case 

 illustrates this difficulty. 



Olearia semidentata Dene, is a moderate-sized xerophytic shrub, which 

 is confined to the moors of the Chatham Islands, where both the climatic 

 and edaphic conditions appear to be of great constancy (Cockayne, 1902. 

 p. 288). The leaves vary on different individuals in size, shape, toothing, 

 and tomentum, and plants grow side by side which, so far as general ap- 

 pearance goes, might easily be taken for distinct species. Probably here 

 the variations are germinal, but at the same time each plant has its own 

 rooting-place* and its individual physiological character, so it cannot be 

 denied but that each plant is subjected to slightly different stimuli to those 

 experienced by any other. 



A most important question is the heredity in fluctuating variations 

 and the degree to which they can be accumulated. Darwin (1899, pp. 31, 

 32) considered them all-important. " These individual differences," he 

 writes, " are of the highest importance for us, for they are often inherited, 

 as must be familiar to every one ; and they thus afford materials for 

 natural selection to act on and accumulate in the same manner as man 



* The importance of the rooting-places of individuals is generally neglected by 

 plant-ecologists who define the conditions of the habitat as a whole, whereas species 

 growing side by side may be subjected to quite different influences, as in the case of 

 shallow- and deep- rooting species, erect and prostrate, and so on. 



