318 Mr. A. Murray on the Homologies of 



is a hip whose disk, instead of enclosing the seed all round, lies, 

 like the petal, only on one side ; and the reason is plain. Nature 

 sets us all an example of economy. If she were about to build 

 a house, and the gable of another house would serve for one of 

 its walls, she would never be at the wasteful expenditure of 

 building a second wall parallel to it, but would use the old 

 gable to save space and expense. She has done so in the Coni- 

 fers; shfe has built her wall of disk leaning on the back of the 

 next disk, making its back wall serve for the front of her house, 

 as shown in the section (fig. 17). 



The same one-sided arrangement follows into the seed; but 

 there it appears to be the result of its position and the physical 

 or mechanical consequences of the growth of the parts about it. 

 At first a mere rounded carpel with the apex of the pistil look- 

 ing downwards, it is soon compressed and flattened by the 

 growth of the scale outside of it and of the neighbouring scale 

 inside of it, and the epicarp dragged forward or pushed up (or, 

 what is the same thing, the growth is inclined in that direction) 

 so as to form the wing; and this in most cases is carried on until 

 it has left the endocarp itself bare on the inner side, and some- 

 times partially and at others wholly bare on the outer side too. 



Looking at the scale in the above light, it may be desirable to 

 note one or two points in its structure and development which, I 

 think, have been overlooked. Not that they perhaps have any 

 bearing upon the question of its being a disk, but merely to 

 make a jotting of the facts. 



In pines and tho^ Conifers which have an exposed apophysis 

 and mucro, the first part of the scale which appears is the mucro 

 of the apophysis. Fig. 9 shows the young female cone of Wel- 

 lingtonia much, magnified; and figs 10 and 11 represent an in- 

 dividual scale seen from the exterior and sideways, with the 

 young seeds hanging from it on the inner side. At this stage 

 it is very apt to deceive the observer as to its homology, seeing 

 that it is not much larger than the male petal, and, like it, ap- 

 pai-ently a continuation of the scale-like leaves of the branch : 

 one^s first idea naturally is that it is the homologue of the male 

 petal; but on examination, besides finding the true claret- 

 coloured petal behind it, we fail to perceive the petaloid texture 

 at the margin ; the margin is not laciniated, and the texture is 

 the ordinary cell-texture of the leaf. 



The subsequent growth of the scale is chiefly from the base. 

 This is the case with leaves too. The point of a leaf never 

 increases much in size ; it is the middle or posterior half where 

 the chief growth takes place. In the male flower we have seen 

 that it is the peduncle which elongates, increasing and extend- 

 ing the dimensions of the anther with it, but carrying on the 



