Cockayne. — Development of Seedlings. 275 



This passing of a plant through three stages, of which the 

 first and the final are not very different, is a phenomenon of 

 extreme interest, to which I have briefly called attention 

 before.* In dealing with the Chatham Island form of P. 

 betulinus — which I may here point out does not go through 

 the semi-shrubby form at all — this matter is gone into at 

 some length, and I propound a theory to account for this won- 

 derful difference between two plants so closely related that 

 botanists up to the present time have not accorded the Chat- 

 ham Island plant even varietal rank.! I will here only point 

 out that the semi-shrubby form much resembles in habit and 

 general appearance the adult form of many New Zealand xero- 

 philous shrubs of dry stations, and of some of which I have 

 already treated.]: In my garden a tree which I grew from 

 seed, now about eight years of age, is shrubby below, with 

 weeping interlacing twigs up to a height of 1*25 m. ; above 

 this for a height of O30 m. the plant is still shrubby, but the 

 twigs are erect and not drooping, while the remaining 045 m. 

 has assumed the final arboreal habit, with thicker hardly 

 flexuous branches passing upwards from the stem at an angle 

 of 45° or less, and with the leaves of the final shape, but not 

 yet of so great size as in an older plant. This appearance of 

 the semi-shrubby form below and of the tree form above 

 persists for a long time, and may be seen in trees long after 

 they have attained to their full development. I do not think 

 that the semi-shrubby portion ever produces flowers, but this 

 is a matter which deserves inquiry. § 



No. 1072. Plagianthus betulinus, A. Cunn. (Chatham 

 Islands var.). Plate XL, figs. 16-20. 



The plants were grown from seed which ripened on a speci- 

 men with seemingly immature fruit kindly given to me by Mr. 

 S. D. Barker, and collected by Mrs. Chudleigh in the Chat- 

 ham Islands. The greater part of the description is drawn 

 up from a number of living seedling and young plants sent 

 to me from the Chatham Islands by Mr. F. A. D. Cox. 



* I.e., p. 358. 



t Kirk, " Student's Flora," 1899, p. 71. Mueller, I.e., p. 10: "Leaves 

 and calyces larger than the specimens in our museum." Buchanan, 

 "On the Botany of the Chatham Islands" (Trans. N.Z. Inst., vol. viii. , 

 1875, p. 334). 



J I.e., pp. 362, 385, 388, 390. It would perhaps be more correct to 

 describe this semi-shrubby form as a transition between these extreme 

 xerophilous forms and a low-growing tree of an ordinary ereot habit. 



§ Goebel states, " Organography of Plants," English edition, Oxford, 

 1900, p. 154, that the fixed juvenile forms of certain Gymnospermse " are 

 usually unable to produce sexual organs, although external conditions 

 are quite favourable for this when they have attained an age and a size 

 at which the normal plants are and have been for long sexually mature." 



