456 OPHIOGLOSSALES 
(Fig. 255 4). There seems to be no fixed type of segmentation of the cells 
which leads to the formation of these sporangiophores, and though, as 
they increase in size, their apex may sometimes be occupied by a 
wedge-shaped cell, more frequently no such cell can be found (Fig. 255 B). 
The subjacent tissue may sometimes increase to a slight degree below 
a young sporangiophore, but it is obvious from the drawings, both of 
transverse and of longitudinal sections, that the sporangiophores are 
derived essentially from the superficial cells. Now this is also the case 
with the sporangia of Opfzoglossum, in which the sporangiogenic band is 
Fic. 255- 
Helminthostachys sep baicd: Hook. A=early phases of sporangiophores. Note the 
variability of size, shown also in the tangential section # Band C=older sporangiophores. 
o oe and G show stages of development of the sporangium, with the sporogenous cells 
shaded. X 200. 
in the first instance composed of superficial cells; thus there appears to 
be correspondence as regards the place of origin of the spore-producing 
members of the two genera. 
Fig. 255 B illustrates the most regular type of these very variable organs ; 
already in the central part longitudinal divisions are taking place which 
indicate the position of the central vascular bundle. The great differences 
in size which they show when young are suggested by the tangential section 
shown as Fig. 255 F. As they develop further the sporangiophores may 
become irregularly lobed or branched. Thus, though disposed with some 
regularity along the margins of the fertile spike, they are themselves very 
variable in size, form, and mutual arrangement. 
It has already been noted also that the position and number of the 
sporangia which they bear is inconstant. In early stages it is impossible 
