156 MINNESOTA BOTANICAL STUDIES. 



occurs near the tip of the frond, so that there is no branching of 

 the stipe. The margins present a more or less wavy, undula- 

 ting outline. In fertile fronds the margins all along the upper 

 part of the frond are prolonged into little leaf-like outgrowths 

 bearing the cystocarps (Fig. 2, PI. 13). These proliferations 

 also occur on the surface of the frond and sometimes are scarely 

 more than the stalk of the single cystocarps they bear. In many 

 fertile fronds the surface is almost entirely covered with these 

 outgrowths. As a rule they occur much more densely on one 

 side than the other. Frequently they are found as simple small 

 leaflets bearing no cystocarps. Their presence gives a look to 

 the lamina quite suggestive of fruiting Calliblepharis. 



■ Internal Anatomy. 



Holdfast. — A section of the holdfast shows a very distinctive 

 structure unlike anything seen elsewhere in the plant. The ap- 

 pearance of a section is seen in Fig. 9, PI. 13, showing the 

 outline of the pit or scar and the depression from which the 

 stipe was removed. The cellular structure varies but little from 

 the general type except in the transition zone from the holdfast 

 to the stipe. Along the upper surface the cells are covered by 

 a gelatinous envelope or cuticle of considerable thickness often 

 15 mic. deep (Fig. 10 a, PL 13). This, of course, in one of the 

 scars extends only to the border of the pit as indicated in Fig. 9, 

 PI. 13. Some sections also show a similar layer on the lower side 

 at joints (Fig. 9 b, PI. 9), while the remainder of the lower 

 surface shows a rough irregular margin of cells (Fig. 9 c, PI. 

 13). The possible explanation suggests itself that the cuticle, 

 when occurring on the lower side, appears at joints which, 

 through some unevenness of the substratum, are not closely ap- 

 pressed to it and hence are left exposed as it were. 



The tissue of the holdfast is characterized by cells having a 

 quadrilateral outline as seen in zone " b" in the right-hand part 

 of Fig. 10, PI. 13. This general type becomes greatly modi- 

 fied in various regions. In the transition zone " c" (Fig. 10, 

 PL 13), from the holdfast to the stipe, the angular outline of the 

 cells disappears and they become more rounded and smaller in 

 size. In all regions cells of irregular outline are frequently 

 met with scattered among the cells of typical quadrilateral out- 

 line. 



In general the cells are arranged in approximately regular 



