Fig. 102 Thalassiophyllum clathrus. A-F, developmental stages to 

 show the origin of the single scroll ( x |). G, adult plant. (After 



SetcheU.) 



only possesses one scroll borne on a solid bifid stipe with tiie vesit- 

 gial scroll on one of tiie branches. It is evident from this description 

 that any branches found on the adult plant are false and represent 

 adventitious outgrowths from the base of the blade. Growth in 

 thickness takes place as a result of the development of a secondary 

 meristoderm as in Laminaria. SHtting is represented by rows of small 

 holes which commence to develop after the first tear has taken place. 



Lessoniaceae : Lessonia (after R. P. Lesson). Fig. 103 



The plants grow erect and form Torests' in relatively deep waters 

 off the shores bounding the southern Pacific, reminding one in ap- 

 pearance of some of the fossil vegetation of the Carboniferous, 



182 



