450 OPHIOGLOSSALES 
were of irregular construction from the first, as above described. It is 
thus seen that in O. pendulum only a comparatively small residuum of the 
original sporangiogenic band finally remains as fertile tissue. Meanwhile, in 
the broad bands of sterile tissue which have thus been initiated between 
the sporangia, vascular bundles make their appearance, connected as 
branch-bundles with the general system of the fertile spike (v. 2, Fig. 249 
D, and Fig. 250): in those cases where the arrangement is regular they 
may occupy a definite position, corresponding very nearly to the point of 
Fic. 249. 
Ophioglossum (Ophigderma) pendulum, L. A, B=transverse sections of spikes of 
different ages to show*sporangia and vascular bundles, slightly enlarged. C=a single 
sporangium, older than in Fig. 248, seen in longitudinal radial section ; the tapetum lightly 
shaded surrounds the darker sporogenous mass. D=tangential section of corresponding 
age, showing one sporogenous mass shaded ; the smaller shaded groups will form the 
vascular strands. #=part of a transverse section of an older sporangium of O. reticu- 
latum. X00. 
intersection of the lines limiting the cell-groups of the original sporangio- 
genic band. In certain cases, where the segmentation is regular it appears 
that one sporangium is referable in origin to two of those cell-groups, but 
it cannot be said that it is always so: frequently the arrangement is 
irregular, and in any case the single sporangium cannot readily be referred 
in origin to a single parent-cell. 
Examination’ of the young spikes of O. vulgatum and reticulatum 
shows that in all essentials the development is the same, though naturally 
with differences of detail and proportion in those less bulky species. In 
them it is also impossible to refer each sporangium to a single parent cell. 
Further, it has been shown in them that the archesporium is not hypo- 
dermal in the strict sense, that is, that it is not cut off once for all by 
one periclinal wall or walls, but that successive additions may be made 
