THE MINNESOTA SEASIDE STATION. 



20: 



,r 



¥lG. lli. A FKUXI' OF Di;SM AI'.I'.STIA I.I'.U.AIA 

 HEEBACEA TAKEN FROM THF; WASH AFTEK A 



Storm. 



Fucus, of which it is taxonomically an ally, and often produces con- 

 siderable beds, though not everywhere abundant like the Fucus. In 

 Figure 11 a group of Pelvetia is 



shown and its habit can easily be I 



recognized. 



Of the low-tide algae there is 

 not only a characteristic segre- 

 gation relative to depth of water, 

 but a careful selection of habits 

 more or less exposed to the in- 

 fluence of the surf and surge. 

 Quite a characteristic group of 

 surf-plants including such kelps 

 as Postelsia palmaeformis and 

 one species of Alaria display 

 themselves where the surf is 

 strongest and seem to require the 

 foaming water of the breakers for 

 their best development. Below 

 these in more sheltered places 

 one finds Hedophyllum, Alaria and Egregia. Below Postelsia, but ex- 

 posed to strong surge, grow the Lessonias, while Pterygophora seeks the 



_. ^ bottom of the surge and N"ereo- 

 I cystis anchors itself in still 

 j deeper water outside the line of 

 breakers. In this outer zone, too, 

 Macrocystis and Dictyoneuron 

 seem to find their best opportu- 

 nities for growth, while Costaria 

 comes somewhat nearer shore. 

 The latter is, however, commonly 

 brought up with the ISTereocystis 

 holdfasts, when they are detached 

 from the bottom. Figure 13 

 shows the exposure of surge- 

 plants at low tide. On the right 

 is Lessonia littoralis. In front is 

 Laminaria bongardiana and on 

 the left is Phyliospadix scouleri. 

 The Lessonia, in particular, is 

 beautifully adapted by its mas- 

 sive trunk and slender leaves to 

 maintain its foothold in the surge and with Postelsia in the surf and 

 JSTereocystis in the deeper water shows in magnificent fashion the work- 



^- 



Fig. 17. Plant of UHOuo.MiiLA Fi.occo.sA' 



TAKEN FROM THE Wa.SH AND PH0T0(;R APHED 



IN A Glass-bottomed Tank. 



