206 PROCEEDINGS OP THE AMERICAN ACADEMY 



be no reason why these structures should not be called by the same 

 name. 



Sclerenchyma fibres occur also in Saccorhiza bulbosa, as I have 

 learned from the examination of specimens in Professor Farlow's 

 herbarium, but they do not seem to be so regularly parallel as in 

 S. dermatodea. They have never been studied by any one, so far as I 

 know. Even the references to them are few. Janczewski* mentions 

 "cellules tres-longues a membrane epaissie simulant des fibres libe- 

 rieuues," in " Haligenia,''^ referring of course to Saccorhiza bidbosa. 

 Kjellman, as I have mentioned above, both describes and figures them 

 for his Phyllaria dermatodea. He says that they are also present 

 (i. e. " the long tubular cells ") in Phyllaria lorea, " but their walls are 

 always thin, not differing in thickness from the walls of the adjoin- 

 ing parenchymatous cells." t 



d. Splitting. — The s[)litting of the frond, although fairly regular 

 and uniform, yet seems to be of the nature of a wound. In some 

 specimens this splitting does not occur at all, but the majority of 

 plants split early. The blade widens, and, being exposed to the buf- 

 fetings of the waves, naturally tends to split. On account of the struc- 

 ture of the fibrous masses of tissue, it splits readily in a longitudinal 

 direction rather than transversely. If the splitting happens when 

 the plant is still young and actively growing, the limiting and cortical 

 layers continue to increase, while the medulla, having no growth of 

 its own, is left behind. Consequently, there is soon a depression or 

 channel formed on the wounded edge. Under favorable conditions 

 the sloping sides of this channel continue to grow until they meet and 

 fuse, and then sections show no trace of the wound. In old speci- 

 mens, however, these outer layers are not growing, and so, when the 

 split occurs in such a frond, the edges exposed simply thicken and 

 harden, and a section always gives evidence of the wound. Almost 

 all the stages between these two conditions are met with. 



e. Fruit. — The last organs to be developed are the reproductive 

 organs. This occurs at Nahant and Peak's Island in the autumn and 

 winter. Specimens just beginning to develop sporangia were found 

 at Nahant in the last part of September, and fruiting specimens are 

 to be found from that time on until May. 



The reproductive organs are borne on the surface of the blaJe in 

 large patches known as " sori." They are of two kinds, zoosporangia 



* Mem. Soc. Nation. Sci. Nat. Cherbourg, Tom. XIX. p. 98 (p. 2 of reprint), 

 1875. 



+ Arct. Alg., pp. 224, 225. 



