Cockayne. — Ecological Studies in Evolution. 27 



The juvenile stage . in these plants, the Taxaceae excepted, does not 

 usually persist for any long period, and may be compared to the first stage 

 in Sophora and the various divaricating shrubs. But in the veronicas, as 

 I have shown, it can be made to persist artificially for years, so long as 

 the plant is kept in moist air. Further, reversion shoots are frequent 

 even on such a typical xerophyte as Helichrysum Selago, while it seems 

 probable that hereditary semi-juvenile races occur of Veronica tetraqonai. 

 Hook, and V. lycopodioides* Hook. f. These are further dealt with on 

 p. 45. In the case of Dacrydium laxifolium Hook, f., a prostrate or 

 suberect mountain-shrub, growing in wet ground or bogs, it is quite com- 

 mon to find juvenile plants with the lax spreading leaves blooming freely, 

 and never developing into the cupressoid adult. The juvenile stage of 

 D. intermedium T. Kirk frequently becomes a tree, and flowers and fruits 

 as abundantly as the " normal " adult growing in the same swamp forest. 

 This flowering juvenile was given the varietal name gracilis by Kirk. 



(3.) Nearly all the divaricating shrubs have a primary juvenile meso- 

 phytic stage. This is generally but transitory, but I have already shown 

 in the case of Pittosporum divaricatum and Corokia Cotoneaster how the 

 early stage may persist in the forest and reach its full stature. Semi- 

 juvenile plants of the Pittosporum may also flower. 



Aristotelia fruticosa Hook. f. (Elaeocarp.) is an interesting case. The 

 early seedling is erect, mesophytic, and, compared with the adult, shows 

 a most remarkable variety of leaves. These are often more or less lanceo- 

 late, toothed, lobed, or pinnatifid (see Plate VII, fig. 1). Later on the 

 divaricating form appears, which may finally be of the most intense cha- 

 racter, the small frequently more or less oblong leaves being scanty, and 

 the ultimate shoots almost spinous. f But this form is not truly stable, 

 plants growing in an adjacent Nothofagus forest being much more meso- 

 phytic. Even when quite in the open, there are forms still divaricating 

 to some extent, it is true, but juvenile so far as leaf-form goes, and these 

 develop no further, and blossom. This semi- juvenile fixed form should 

 be considered older than the " normal " adult, and it may represent the 

 pre-glacial plant. 



Suttonia divaricata Hook, f., so far as I have observed, has no seedling 

 mesophytic stage. But even this " well-fixed " species when growing on 

 the Poor Knights Islands has leaves three times the size of those of the 

 usual stations. 



(4.) Nothopanax simplex Seem, and N. Edgerleyi Harms. (Araliac.) have 

 also a mesophytic juvenile form, but the adult must be considered meso- 

 phytic likewise. Both are rain-forest plants, while the former is found 

 also in certain subalpine scrub. I have not full details regarding N. Edger- 

 leyi, the juvenile form of which sometimes so closely resembles that of 

 N. simplex that I, for one, cannot distinguish between them, so my remarks 

 are confined to the latter species. The early stage has a fern-like, much- 

 cut, thin and large leaf. This is succeeded by a second stage with ternate 



* Cheeseman found a semi-juvenile form of V. tetrarjona at the base of Tongariro 

 and Ruapehu, and writes (1908, p. 281), " Probably it is an intermediate state between 

 the juvenile stage and the fully matured one, but if so it must persist for many years." 

 Mr. Poppelwell collected a form of whipcord Veronica on the Garvie Mountains, a plant 

 of which has kept the semi- juvenile form for two years in my garden. So, too, from 

 some notes sent to me by Mr. F. G. Gibbs it is evident that he has had in cultivation a 

 very similar plant. 



f Hymenanthera dentata R. Br. var. alpina T. Kirk also develops 6emi-spines under 

 very dry conditions. 



