No. 505] KFLl'S AM) UFA .1 FI T I LA 77 OA TI1FOL V '-.) 



mately 2.',] mm. in length and the margin of the primitive 

 disc was nearly smooth. The edge of the lamina was only 

 one cell in thickness, hut there were evidently several lay- 

 ers in the middle region and toward the base. In a spec- 

 imen 6.5 mm. long the holdfast had become distinctly 

 crenate around the edges and the one-layered lamina 

 had disappeared. The crenations had become much more 

 pronounced and had assumed the characters of primary 

 hapteres in a specimen 10 mm. long (Fig. 6). 



By the time the plant reaches the length of an inch its 

 determination is not difficult. A specimen 2S nun. long 

 (Fig. 37) will serve for comparison with the youngest 

 Egregia described. The lamina is narrower and longer 

 than in that plant; the holdfast has not as yet developed 

 secondary hapteres and the stipe is shorter. Though the 

 stipe always remains short, it usually becomes longer 

 than is shown in this plant (about 5 mm.). The narrow- 

 ness of the lamina is characteristic, but is not sufficiently 

 marked at stages earlier than this to render diagnosis 

 easy. 



Soon after this stage secondary hapteres begin to ap- 

 pear above the primitive holdfast. Though they arise in 

 circles as in the other kelps, they usually develop quite 

 unevenly in the young plant, some members of the circle 

 becoming long, while others are yet mere knots on the 

 stipe. When a length of about 8 cm. is reached the stipe 

 begins to thicken and flatten. The transition region, 

 which has been sharply marked off, becomes less and less 

 distinct and the plant comes to consist of a lamina with a 

 cuneate base anchored by the holdfast (Fig. 42). This 

 condition sometimes persists until the plant has reached 

 a considerable size. More usually, however, the broaden- 

 ing continues and quickly brings about the adult condition. 



When mature (Fig. 43), Hedophijllum sessile becomes a 

 broad, cordate, sessile plant anchored by a mass of hap- 

 teres at its base. Its lamina is torn to ribbons like a digi- 

 tate Laminaria, so that it mav resemble one of the 

 kelps with true branching. The hapteres arise in circles 

 one above the other higher and higher up on the stipe 



