62 NEW ZEALAND PLANTS. 



Sow the seed of Sophora grandiflora. Again comes the small, 

 erect plant ; but this is succeeded by no shrubby, dense form : the 

 young plant continues its development without noticeable change 

 until it is fully grown into a tree. Finally, sow seed of Sophora pro- 

 strata. Again the upright early seedling appears, then the juvenile 

 shrubby stage, as in S. microphylla ; but this time it never develops 

 into a tree, but has this shrub stage as its adult form. Finally, with- 

 out going into further details, there are about two hundred New Zea- 

 land plants which have adult forms differing considerably from the 

 juvenile, many of which can, when fully grown, revert to the early 

 form. 



Now, it is held by certain biologists than an organism in its indi- 

 vidual development passes, more or less completely, through the 

 stages assumed by the species at various times during its past evolu- 

 tionary history. If this is so, then juvenile stages represent ancestral 

 stages, and such a plant as the seedling whipcord veronica, with leaves 

 of the above-mentioned experiment, is the ancestor of the present 

 river-terrace V. cupressoides, artificially brought back into the world, 

 and kept so long as the moist-air treatment continues. This treat- 

 ment, too, shows that the ancestral plant lived in a much moister 

 climate than is New Zealand at the present time. The behaviour 

 of Sophora, too, throws some light on the matter. The very earliest 

 stage would be the ancestral form ; but as this is the same in both 

 S. grandiflora and S. microphylla, the former is ancestral from begin- 

 ning to end of its development, whereas the latter, in its middle stage, 

 exactly resembles S. prostrata. 



All this points out that there came a period of drought in New 

 Zealand, or of a climate requiring drought-resisting adaptations. 

 Then certain adaptations against excessive dryness came into being, 

 as in the cases of the shrubby form of Sophora and the adult of 

 Veronica cupressoides. On a more recent change to a wetter climate 

 some individuals of the former genus would grow out of this drought- 

 resisting form, others would remain unchanged ; but in the case of 

 the veronica no reversion has taken place, but the " ancestral form ' 

 still remains latent. 



