﻿Douglas Spruce, Pseudotsuga mucronata 9& 



in the thickest part of the cone, paralleling in this regard the case 



of the normal cone. 



Below the base of the cone for the distance of I cm. are found 

 foliage leaves with acute apices (Fig. 15). Further still below, the 

 leaves approach more closely to the normal shape (Fig. 14), but 

 still differ in having somewhat acute apices (Fig. 20). 



The leader involved is bent so as to suggest that some accident 

 overtook it during its growth. The bracts are quite sharply bent 



(F 



fortune. At 



and lateral buds which developed in the usual way the following 



spring. 



We have, then, in the structure upon which the above descrip- 

 tion is based the result of the sudden assumption of the sporophyl- 

 lary function by the tissue of a normally strictly negative shoot. 

 We have here to do with the question which has grown out of 

 Bower's * view that foliage leaves are secondary structures pro- 

 duced by the sterilization of the sphorophylls. 



Bower has been followed by Atkinson,! who has attacked the 

 problem from the point of view of the experimental morpholo- 

 gist, and has discussed the relation of the sporophyte to nutn- 



^ . ... . •.•-_:-4.u^ moWoi- atv» ha<;pH to a 



tion. Professor Atk 



nun. rruicssor niKinsuu a wuvn-tiuiw - 



considerable extent upon experimental work upon two species of 

 Onoclea, in which the sporogenous leaves were made to take on 

 the assimilative condition by cutting away the earlier and normally 

 assimilative leaves and thus robbing the plants of food which they 

 would otherwise get. The condition thus induced is compared 

 directly with the probable conditions under which the sporophyte 

 was made to assume more and more the assimilative function 

 when the change from water to dry land was one with which the 



gametophyte was unable to cope. 



The conversion of a vegetative shoot in a conifer to a sporo- 

 phyll-bearing shoot is of peculiar interest in this connection in that 

 it must have some bearing upon the view propounded by Bower 

 In the coniferae only a few lateral budsjrejionnally_ produced 



*Bower : «A Theory of the^biluThTAichegoniate Plants." Ann. Bot., 8 



343- 1894. 



t Atkinson : Woods Holl Biol. Lect. i8 9 5- Am - Nat 3 ° : My ' ^ 



