HOW TO KNOW THE SEAWEEDS 



29a Thallus showing a gradation from a multiseriate (polysiphonous) 

 condition to a uniseriate condition in the ultimate ranks of branches. 

 Figs. 46, 47 Heterosiphonia 



Figure 46 



Fig. 46. Heterosiphonia erecta Gardner, emend. Setchell & Gardner 



A small upper part of a plant to show the uniseriate ultimate 

 branchlets arising from multiseriate branches of the prior order. Note 

 the pecuhar antheridial branchlets on this plant with their minute sper- 

 matic. This is a common small species along southern Cahfornia. The 

 only large, conspicuous member of this genus in the United States is 

 H. gihbesii (Fig. 47). 



Fig. 47. Heterosiphonia gibbesii (Harvey) 

 Falkenberg 



A small upper portion of a plant, X 1.25. 

 This is the largest species of the genus in 

 our flora, occurring in Florida and reach- 

 ing 10-20 cm. in height. 



48 



