THE ADULT SPOROPHYTE 



91 



ctWm O.moluccanummzy therefore be described as a three-sided or four-sided prism 

 or a truncate pyramid. 



As m the young plant, the stipular sheath of each new leaf is formed mainly 

 from the basal tissue of the leaf itself, but includes also tissue from the margin of 

 the stem apex. The sheath is open above by a narrow pore through which it 

 communicates with the space between it and the next stipular sheath. In 0. 

 moluccanum, as in 0. vulgatum, three leaves of different ages can generally be seen 

 inclosed in the bud and sometimes the first indication of the fourth young leaf can 



B 



Fig. 57. 

 Six of a series of cross-sections from a sporophyte of Ophioglossum moluccanum. sp, young sporophyll; x^ stem apex. 



also be distinguished (fig. 56, C,D). A cross-section of the youngest sheath shows 

 the pore as a minute opening, separated from the stem apex below by a very 

 narrow space. 



A careful study of the older stem gives no reason for assuming that the tissues 

 of the very open reticulum forming the fibrovascular system of the rhizome is in any 

 part due to additions from the apical tissue of the stem. Whether longitudinal 

 or transverse sections are examined it is perfectly clear that the strands of this 

 reticulum are made up entirely of leaf traces which can be readily followed into the 

 young leaves or the tissue immediately below. The immediate apical region of the 

 stem, as in the younger sporophyte, is unmodified parenchyma which adds only to 

 the large central pith, if pith this can be called, as the separate bundles of which the 

 vascular reticulum is composed run free for long distances through the ground tissue 



