ON THE THEORY OF VEGETABLE SPIRALS. 367 



respect to the absence of a tap-root and to the tendency to put 

 out adnate roots, but also as relates to Mohl's discovery of the 

 crossing of the vascular bundles or fibres; a discovery which 

 might, I think, have been anticipated by an attentive considera- 

 tion of morphological principles; or which, at any rate, now 

 that it has been made, seems to confirm them. Figure* (3) is 

 intended to illustrate what has now been said, and we shall see 

 hereafter that the same view is confirmed by a consideration of 

 the leaves of this class of plants. That they stand lower in 

 point of organization than dicotyledons is admitted by every 

 one, and seems to be indicated on the principle we have already 

 noticed by their tendency to put out roots above the ground as 

 well as by many other circumstances, and we seem to be justified 

 in inferring from this that the spirals which are numerically 

 more complex are really types of higher organizations. 



It may be well, in order to obviate a misconception of my 

 meaning, to explain what has been said as to upward and out- 

 ward growth in dicotyledons. No doubt the stem or trunk of 

 any tree belonging to this class is a portion of a conical surface 

 whose apex is above the ground and not below it, and the same 

 is true of the surface of contact of cambium and wood, that is, 

 of the surface where fresh wood is, at any given moment, in 

 process of being formed, so that in one sense the growth is up- 

 wards and inwards. But the corresponding conical surface a 

 year ago lay within and below the other, so that the transition 

 from the one to the other is outwards as well as upwards, and 

 that it takes place in a spiral as if the surface turned on its axis, 

 and at the same time enlarged, may reasonably be presumed in 

 accordance with the views which I have been endeavouring, 

 though with much diffidence, to support. Of course it is not an 

 objection to these views to say that the woody fibre does not 

 consist of spirals, actual growth being one thing and the de- 

 velopement of forms, or what may be called ideal growth, an- 

 other. 



5. In endeavouring to apprehend the process of transition 

 from one kind of spiral to another, it is difficult in the present 



* The figures (2) and (3) referred to in the text, were not to be found among 

 the papers placed in the Editor's hands : fig. (2) on page 365 has been drawn by 

 the Editor, who is however unable to infer with any confidence the form of the lost 

 figure (3). 



