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THE AMERICAN NATURALIST [Vol. XLIII 



But further growth is for a time almost restricted to the 

 lamina until the ratio is increased to ten or fifteen to one. 

 After this stage the stipe begins to grow and soon sur- 

 passes the lamina, which seldom exceeds half a meter in 

 length, while the stipe sometimes becomes fifteen or 

 twenty times as long. 



A specimen 12 cm. in length (Fig. 32) though only two 

 thirds as long as the one just described, was considerably 

 more advanced. The uppermost quarter of the lamina 

 was entire, as in the last plant, and below the tip were a 

 few serrations like those at the extreme base of the 

 former. Toward the growing point these outgrowths were 

 larger and had become spatulate proliferations about a 

 centimeter long, fringing the basal two thirds of the blade. 

 The stipe had reached a length of 3 cm. Its numerous 

 tubercles were much elongated and frequently dichoto- 

 mously branched, once or even twice giving the peculiar 

 roughened appearance characteristic of the adult. The 

 proliferations along the lateral edges of the stipe were 

 much more numerous than in the former specimen ; some 

 of them were simple laminar appendages ; others were in- 

 flated into small globular pneumatocysts (Fig. 31, p) ; on 

 others the stalks were roughened by small tubercles like 

 those of the main stipe. Some of these last, if detached, 

 might easily pass for young plants cut off just above the 

 holdfast. 



Though marked changes are yet to occur before the 

 plant becomes mature, they may be understood by a com- 

 parison of the adult with this young plant (Fig. 32) . The 

 most conspicuous change is of course the great elonga- 

 tion. While this is especially noticeable in the stipe, the 

 lamina likewise grows until it reaches a length of about 

 50 cm., but its width increases scarcely at all, seldom ex- 

 ceeding 4 cm. The proliferations from this narrow 

 lamina become so numerous that they completely mask 

 the distinction between it and the stipe, and it is only by 

 close inspection that the lamina may be recognized. The 

 growth of the stipe carries the lamina far away from the 

 holdfast, where it is exposed to the severest action of the 



