66 Chlorophycece 



Order II. CH^ETOPHORALES. 



In this order of green Algae the thallus is filamentous, sometimes 

 simple, but more frequently branched. The brandies are generally 

 attenuated and often piliferous. The cells possess one nucleus, 

 and in all the families of the order, except the Trentepohliacese, 

 there is a single parietal chloroplast with one or more pyrenoids. 



Asexual reproduction takes place often by resting-spores, which 

 may be either aplanospores or akinetes, and commonly by zoogonidia 

 with two or four cilia. Sexual reproduction is brought about by 

 isogamous planogametes with two cilia, or by well-differentiated 

 heterogamous gametes. 



This order has also received the name of the " Ulotrichales," 

 but I prefer to accept Wille's name of the " Chastophorales " as 

 five out of the seven families include branched Algae. 



Family 1. Coleochcetacece. Flat expansions or pulvinate branched 

 masses, epiphytic on the stems and leaves of submerged plants. Sexual 

 reproduction heterogamous ; plants monoecious or dioecious ; oogonia 

 with a trichogyrie and one non-motile oosphere; fertilization within 

 the oogonium and resulting in the formation of a cortical layer on the 

 outer surface of the oogonium. Some of the cells of the thallus are 

 furnished with fine bristles with basal sheaths. 



Family 2. Herposteiracece. Filaments branched, creeping, epi- 

 phytic on submerged plants. Sexual reproduction heterogamous; 

 plants monoecious ; oospheres motile, fertilization taking place outside 

 the oogonium. Cells with one or several long bristles, sometimes 

 swollen at the base. 



Family 3. Vlotrichacece. Filaments simple. Chloroplast single, 

 parietal, with one or many pyrenoids. Sexual reproduction isogamous. 



Family 4. Cylindrocapsacece. Filaments simple ; cells with thick 

 lamellose coats, usually arranged in a single series within a lamellose 

 gelatinous sheath. Sexual reproduction heterogamous ; plants monoe- 

 cious ; oogonia with one non-motile oosphere ; fertilization within the 

 oogonium. 



Family 5. Chcetophoracece. Filaments branched ; branches attenu- 

 ated into multicellular hair-like prolongations. Chloroplast single, 

 parietal, with one or many pyrenoids. All the cells except those of the 

 rhizoids and hairs are capable of producing zoogonidia or gametes. 

 Sexual reproduction isogamous. 



Family 6. Microthamniacece. Filaments branched ; branches 

 scarcely attenuated, not piliferous. Chloroplast single, parietal, with 



