OF ARTS AND SCIENCES. 



197 



branches in the one or two specimens of this period which showed 

 them, and so a more complete account of them is left until the next 

 period is discussed. 



Tiie stipe, towards the end of this period, hecomes a rather solid 

 structure, composed of the following tissues. Outside is a limitiii*.' 

 layer similar to that described for the blade, but vvhicli is in a state of 

 more active growth. The cells composing it are somewhat elongated 

 radially, and divide actively by tangential walls. By divisions in the 

 two directions perpendicular to this, it also keeps pace with the growth 

 of the stipe in circumference and length. Within this are several 

 layers of cortical cells, and the centre is occupied by a mass of 

 elongated tubes. No liyphal cells are present except at the transi- 

 tion place. 



All except one of the younger specimens had lost the point of at- 

 tachment. This individual is 6 mm. high. The base is decidedly 

 bulbous, and is 18 mm. wide, while the stipe above is about 0.1 mm. 

 wide. The bulbous base is about 0.13 mm. high. At the bottom it 

 is attached by a number of hair-like bodies, which it seems proper to 

 term rhizoids. These are comparatively numerous (probably between 

 50 and GO), and arise as prolongations from the cells of the limiting 

 layer of the basal portion of the enlargement. The rhizoids them- 

 selves are irregularly cylindrical, and at this stage seem to be for the 

 most part unicellular. Toward the distal end the shape is more ir- 

 regular, the wall thicker and wrinkled, and at this portion too they 

 are not infrequently and somewhat irregularly branched. The branches 

 are very short and the tips of the rhizoids are somwhat swollen. This 

 specimen was growing among a mass of other young plants and fine 

 filamentous forms of other species, and this allowed the rhizoids to be 

 seen to greater advantage. 



The above description is to a certain extent fragmentary, but much 

 of that is due to the character of the available material. That previ- 

 ous to this period there exist stages in which the frond consists of a 

 simple membrane of a single layer of cells seems to be evidenced by 

 the fact that, in the youngest specimen seen, the blade is for the greater 

 part in that condition. It is supported, too, by what we know of the 

 early stages of some nearly related species. What the stages are by 

 which the development proceeds from this simple frond to such a stage 

 as that represented by the youngest specimen described is largely a 

 matter of conjecture. That the complexity comes about by a series 

 of definite and gradual changes seems probable. It is supported, 

 moreover, by what is desi-ribed above. For in the blade we find at 



