Cockayne. — Ecological Studies in Evolution . 25 



the adult has appeared. Should such a flowering juvenile form be ephar- 

 monic, then, as Diels has shown, we are face to face with a case of onto- 

 genetic evolution (1906). In some of the species the juvenile and adult 

 forms can both clearly be shown to be epharmonic (e.g., Veronica lyc&po- 

 dioides Hook, f., Carmichaelia subulata T. Kirk, Discaria toumatou Raoul r 

 Potamogeton Cheesemanii A. Bennett, Clematis afoliata Buchanan) ; they 

 can even be experimentally produced or prolonged. In other cases ephar- 

 mony can only be inferred (Sophora microphyUa, Podocarpus dacrydioides? 

 Rubus schmidelioides) ; and in others it is more or less obscure (Parsonsia 

 heterophylla, Pseudopanax crassifolium C. Koch, Pittosporum patulum 

 Hook. f.). There is, therefore, a gradual gradation from the known to the 

 unknown, but, as the main features are alike throughout, it is reasonable 

 to assume an epharmonic origin in most cases, notwithstanding that con- 

 tradictory examples occur, and to consider that there is a relation between 

 the age of the form and its relative stability. Here there is no attempt 

 to go thoroughly into the phenomenon under consideration ; certain typical 

 examples are alone discussed. 



The significance of the divaricating growth-form has been already noted. 

 It may be remembered it is eminently xerophytic, extremely well defined, 

 and present in various unrelated families. But this form is not confined 

 to shrubs alone, but appears as a persistent juvenile stage in the life-history 

 of certain plants, which are thus xerophytic shrubs for some years and 

 finally ordinary mesophytic forest-trees. The. following are examples : 

 Pennantia corymbosa Forst. (Icacinac), Hoheria angustifolia Raoul, Plagi- 

 anthus betulinus A. Cunn. (Malvac), Sophora microphyUa Ait. (Legum.), 

 Elaeocarpus Hookerianus Raoul (Elaeocarp.). 



The case of Sophora microphyUa Ait. is the most instructive. It must 

 be considered along with the remaining species — S. tetraptera* J. Mill., 

 S. grandiflora Salisb., and *S. prostrata Buchanan. All the species com- 

 mence with hypogeal cotyledons, and the first, or first two, leaves are 

 simple and arrested structures, but the succeeding ones are pinnate and 

 of the adult type. The primary stem is erect and somewhat flexuous (see 

 Plate VI, fig. 2), except in the case of S. grandiflora. This species 

 continues to grow erect, and in time develops into a small tree. There 

 is no heterophylly beyond the early simple leaves, and no hint even of 

 any xerophytic shrub stage. With S. microphyUa the progress of events 

 is very different. Here the early seedling soon develops into a xerophytic 

 divaricating shrub, and so it will remain for some ten years or more, and 

 attain a height of perhaps 1-4 m. before the more or less erect branches 

 shoot upwards, the forerunners of the mesophytic tree form (see Plate III, 

 fig. 1). It is quite common to see a specimen which is shrub at the 

 base and tree above. Occasionally the upper part of the shrub form will 

 blossom, but I do not think this ever happens before the tree itself 

 flowers. Sophora prostrata never grows out of the shrub state ; it is a fixed 

 juvenile form, which, moreover, reproduces itself true from seed. Between 

 S. microphyUa, and S. prostrata there are intermediates. With regard 

 to *S. tetraptera, the juvenile plant differs but little from the adult (see 

 Plate VI, fig. 1), though it has for a time a few flexuous twigs. I have 



* Under this name I include the Chatham Island plant, a form in the neighbour- 

 hood of Auckland City, and the Chilian plant. As for the Auckland plant, I do not 

 know its juvenile state well enough to speak with certainty, but in any case its behaviour, 

 if different from that stated, would not in any way affect my conclusions. 



