CHAPTER XII. 
SPORANGIOPHORES AND SPOROPHYLLS. 
THE theoretical position taken up in the last chapter is characterised not only 
by its simplicity but also by its elasticity. It carries with it no obligation 
to assume that all the appendicular organs should show definiteness or 
constancy in their disposition upon the axis which bears them, nor even 
that they were all alike in ‘their initial character or function. Now, as a 
matter of fact, an examination of the strobili of such plants as the Psilo- 
taceae, Horsetails, and Calamarians shows that 
irregularities of arrangement of the parts are 
common: it is impossible to reduce the 
arrangement of the appendages in the cone of 
Tmesipteris or of Equisetum maximum to any 
regular scheme (Fig. 73): the appendages of 
both vary in radial angle and in level of 
Ca insertion. There is also great variability in 
07) the disposition of the leaves in the genus 
Lycopodium, being sometimes whorled, some- 
times irregularly spiral. It is true that cases 
: do exist among the strobiloid Pteridophytes 
Transverse section through a spor- ‘ 3 zs 5 <8 
angiferous bud of Yyesifteris. ax= Which show regularity in the disposition of 
axis. /=foliage leaves. /=lateral a 5 : 
lobes. “sy=synangia. X20. their parts, but in their shoots at large a 
regular disposition of the appendages cannot 
be held to be a general feature. Such irregularities, so far as they are 
of primary origin, are difficult to explain on the basis of any sympodial 
construction of the strobilus: to a theory of enation, as expounded 
in the previous chapter, they offer no obstacle; for if the appendages 
originated from the surface of the pre-existent axis, as suggested, they 
might equally well appear in regular positions, or be disposed with greater 
or less irregularity—as, indeed, is seen to be the case. 
The comparative classification of those appendages of the strobilus 
which are seen in the different types of Pteridophytes has always presented 
Fic. 73. 
