208 Barratt. — A Contribution to our Knowledge of the 
the genus, and has also been shown to occur in all the stems of Calamites ; 
it may therefore be considered as a relatively primitive character, since it is 
common to both living and fossil representatives. 
Origin of the Secondary Axis. 
Provision for the first branching is made very early in the history of 
the primary shoot, even while the latter is still enclosed within the folds of 
the prothallus. 
Hofmeister (3), in his classical account of Vascular Cryptogams, figures 
a young sporeling with the 
first lateral bud pushing its 
way through the tissues of the 
mother axis. He undoubtedly 
considered this bud to have an 
endogenous origin, but did not 
comment upon it in particular 
because at that time all the 
lateral buds of Equisetum were 
thought to arise from the cen- 
tral tissues. 
It was later shown by 
Janczewski ( 8 ) and Vidal ( 6 ) 
that the whorled aerial branches 
take their origin from buds 
which arise from superficial 
cells of the stem at the base 
of the leaf-sheaths. It was 
consequently assumed that all 
the lateral buds arose in like 
manner. 
Text-fig. 5. Transverse section from base of 
primary axis showing origin of the first bud. The 
apical cell is already established, although the xylem of 
the primary stem is not yet differentiated, x 950. 
Jeffrey (4), however, in 
his description of the sporeling, 
refers to its position low down 
on the axis well below the leaf-sheath, and speaks of it as the £ so-called 
adventitious bud ’, but does not make it clear whether this expression refers 
to its position on the axis or to its endogenous origin. 
In order to determine the latter question, sporelings were sectioned in 
various directions. It was found that the bud initial is formed at a very 
early stage in the history of the primary shoot, in fact as soon as the first 
leaf-sheath is organized. From an examination of Text-fig. 5 , one of 
a series of transverse sections, it is seen that the bud is undoubtedly endo- 
genous and probably originates in the layer which gives rise to the 
endodermis. The young branch develops slowly and gradually pushes its 
