CHAPTER XV. 



ANATOMICAL EVIDENCE. 



IN the previous chapter it has been shown that early embryological detail 

 is an insecure guide for purposes of comparison : that segmentation is not 

 related with any general constancy to the origin of the appendages : also 

 that the anatomical regions of the mature part are not defined with any 

 constancy by early segmentations at the apex. It remains to enquire in 

 what way the anatomical characters of the mature parts will affect the 

 questions discussed, and especially whether they tend to support or to 

 refute the strobiloid theory as put forward in Chapter XI. 



The most pregnant change in anatomical view effected during the last 

 half century has been caused by the introduction of the Stelar theory of 

 Van Tieghem. Prior to it the individual vascular strand, pursuing its 

 course from the appendage into the axis, was regarded generally as the 

 structural unit of the vascular system of the whole shoot. This was a 

 natural consequence of that detailed investigation of the course of the 

 individual vascular strands which was initiated with such success by 

 Naegeli, and extended by many other writers'. The position taken up by 

 these observers is admirably summarised in the Comparative Anatomy of 

 De Bary : from his account it will be seen that the method of anatomical 

 study, as well as its result up to 1877, was such as to give prominence 

 to the individuality of the leaf: the facts as there stated might almost be 

 read as an expression of phytonic theory in terms of internal structure, 

 since the chief aim was to follow downwards to its termination each 

 individual strand of the leaf-trace. A phytonic view of the facts was 

 never explicitly set down by De Bary, though the under-current of 

 thought seemed clearly to lead to an analytical rather than an integral 

 view of the construction of the shoot. 



But very soon this was corrected, on general and external grounds 

 rather than on those of anatomy, by Sachs : for in his Lectures on the 

 Physiology of Plants (1882), he strongly insisted on the contemplation of 

 the shoot as a whole. It is impossible to say how far this may have 



