PHTCOPHTTA. 



157 



(Ji) White Rusts occur on many plants : one (Albugo Candida) on 

 sliepherd's-purse, peppergrass, radish, etc.; another (A. bliti) on 

 Amaranthus ; and another (A. portulacse) on purslane. For conidia 

 make very thin cross-sections of leaves, through a white-rust spot, 

 and mount as above. The resting-spores (vphich are dark brown) are 

 easily obtained in the leaves of Amaranthus and purslane. 



Systematic Literature. — Wolle, Freshwater Algae of the United 

 States, 146-154. Saccardo, Sylloge Fun^orum, 7'. Flora of Ne- 

 braska, 1 : 53-60, pi. IS, 13, 15, 16. 



Okdbr 6. CONFERVOIDE.ffi;. The Confekvas. 



277. These are always multicellular, green plants, with 

 the cells mostly arranged in simple or branched filaments, 

 rarely arranged in a plate or membrane. ISTo species are 

 hysterophytic. The gametes are equal and motile in the 

 lower families, but in the higher ones they consist of 

 antherozoids and fixed oospheres. 



278. The Sea-lettuce (Ulva, Pig. 86, A), which is com- 



FiG. 86.— ^, a plant of Sea-lettuce (Ulva lactuca). Natural size. B, a 

 young plant of ulothrix zonata. 1, escape of asexual zoospores ; 2, sexual 

 zoospores. X 200. (From Strasburger.) 



mon along the coast and in brackish waters, growing upon 

 stones, wharf -timbers, etc., and resembling small lettuce- 



