A Monograph of tlic Genios Alariu. 73 



f. cUstans Miy. et Okam., quite approximate in f. typica Yendo and 

 confluent with in f. nandensis Yendo. Wliatever the gradations 

 may be in the separation of the sporophylls from the sterile blade, 

 the essential difference between the sporophylls of Alaria and Undaria 

 is in the degree of their differentiation. In the former they are 

 separated into a number of petiolated leaflets^) while in the latter 

 they are continuous and directly confluent with the stipe edges. 

 Ilirome undarioides Yendo shows a step more primitive in this 

 respect than Undaria. 



Alaria, Undaria and Ilirome have the true midrib. There are 

 costated members among the family LaminariaceaD, such as Acjarum, 

 which, however, must by no means be regarded as standing near 

 to them. Ptcrygopliora, which is acknowledged to have the closest 

 relationship with Alaria, is not provided with the true midrib. 

 Yet its presence in the three named genera must never be passed 

 over as merely incidental. 



The mucilage glands, again, as far as has hitherto been ob- 

 served, are limited to Alaria, Undaria, Hirome, and Laminaria 

 Pelerscniana Kjellm. The last mentioned species has neither mid- 

 rib nor sporophylls. On the other hand, it has various peculiarities 

 to be counted under the genus Laminaria. Okamura's idea to 

 comprise it in Undaria together with Hirome is hardly acceptible 

 before we have extended the limitations of the other genera of 

 Laminariace96. 



Leaving L. Pelerscniana Kjellm. aside for the present, the 

 three genera, Alaria, Undaria and Hirome, form a continuous series, 

 and the genus Pterygophora stands near Alaria in another direction. 



Setchell'2) holds the view that " the nature of the outgrowths 



1) There are various degrees in separation oE the leaflets; compare .1. Pylaii (PI. VII, fig. 1) 

 with A. mncroplera (PI. IT, fig. 1). and A. angusta (PI. XV, fig. 1). 



2) Setchell : Post-Embryonal Stages of Laminariace;e, p. 120. 



