HOW TO KNOW THE SEAWEEDS 



173b Medulla composed only of large, parenchymatous cells 174 



174a Cortex of 2 to 3 tiers of small cells, not in vertical (anticlinal) rows 

 except sometimes in tetrasporangial sori. Fig. 218 175 



Fig. 218. Rhodymenia sp. 





Part of a transection of a blade 



Figure 218 



^(^ to show the way in which the cor- 

 tical cells do not present an ar- 

 rangement in anticlinal rows. 



174b Cortex of more than 3 tiers of small cells arranged in anticlinal 

 rows. (This may be true in Phyllophora, step 177b only in older, 

 thicker parts of blades where secondary growth of the cortex oc- 

 curs.) 177 



175a Cystocarps embedded in the medulla, arranged so as to form a 



linear sorus resembling an interrupted midrib. Fig. 219 



Stenogramme mterrupta 



Fig. 219. Stenogramme inter- 

 rupta (C. Agardh) Montagne 



An upper portion of a female 

 plant showing the appearance 

 of the cystocarps in linear sori, 

 X 0.8. Tetrasporic plants have 

 the sporangia in small, irregu- 

 larly shaped, nemathecial sori 

 scattered over the flat faces of 

 the blades. This is the only spe- 

 cies of the genus on our coasts. 

 It may be encountered in drift 

 or at low intertidal levels along 

 the entire Pacific shore. 



Figure 219 



164 



