(80) 



II. THE STEM OR SHOOT* 



Included under this heading are, firstly, the ordinary 

 leafy stem and its branches such as we see it, e. g. in 

 any ordinary plant, and secondly, the hypocotyledo- 

 nary stem (hypocotyl), viz., that portion of the axis 

 which intervenes between the cotyledons and radicle 

 in every seedling. All other structures which techni- 

 cally come under this heading, but which have become 

 involved in the building up of the compound organ 

 known as the flower, will be treated of under the 

 heading of that organ. 



Many and varied are the forms and other characters 

 of the stem even in quite normal circumstances, and 

 many of these, as will be seen in the course of the 

 following pages, offer an interesting parallel to the 

 variations which occur as a result of abnormal ten- 

 dencies. 



The stem or shoot may become abnormal either as 

 regards its form or its position. 



There will now be described the different types of 

 abnormal tendencies exhibited by this protean organ. 

 These may be distributed under four main headings, 

 viz.: (1) Differentiation; (2) Simplification; (3) 

 Change in Direction of Growth ; and (4) Adventitious 

 Origin. 



1. DIFFERENTIATION. 



The abnormal growth assumes the form either of 

 lateral branching or of an extension of the vertical 

 growth of the main shoot. 



* Latin caulis. 



