8 Weiss, Root-apex and Young Root of Lyginodendron. 



the root-tip. But, as I have endeavoured to show in this 

 paper, this and other longitudinal sections through root- 

 apices which I have since examined seem to me not to 

 be quite median, and as the meristematic cells are small, 

 it is more probable that the absence of a definite apical 

 cell in the section is to be attributed to the somewhat 

 tangential nature of the section than to the absence of 

 a single apical cell. This conclusion is based upon the 

 examination of transverse sections which pass close to 

 the apex, and in which the regularity in the arrangement 

 of the tissues suggests a structure of the apex resembling 

 that of recent Leptosporangiate Ferns. Of course it is 

 possible that the more delicate lateral rootlets like those 

 described above possessed a single apical cell, while the 

 more massive adventitious roots emerging from the stem 

 were provided with a group of initials. Our knowledge 

 of root- tips of the recent Osmundaceae makes such a 

 suggestion possible. As attention has now been drawn 

 to the occurrence of these young root tips, it is probable 

 that other observers may be able to supplement the 

 information given above, and truly median longitudinal 

 sections may be found from which we can conclusively 

 prove the existence or non-existence of a single apical 

 cell. 



