GEOUP I. THALLOPHYTA : ALGJ} : PH.EOPHYCEJE. 257 



The Phaeophyceae may be classified as follows : 

 Unicellular Forms : 



Order 1. Syngeneticaa '. no sexual reproduction. 



Order 2. Diatomaceaa : sexual reproduction isogamous by aplauogametes. 

 Multicellular Forms : 

 Series (a) Phaeosporeae : sexual reproduction isogamous by planog*metes ; 



asexual by zoospores (in some cases by zoogonidia). 

 Order 3. Ectocarpaceae : including the families, 



Ectocarpeae (Ectocarpus, Pylaiella, Streblonema, etc). 



Choristocarpeae (Choristocarpus, Discosporangium) . 



Myriotricheae (Myrotrichia). 



Myrionemeae (Myrionema, Microspongium, etc.). 



Elachisteaa (Elachista, Giraudia, etc.). 



Desmarestieae (Desmarestia, Arthrocladia). 



Spermatochneae (Spermatochnus). 



Sphacelarieaa (Sphacelaria, Stypocaulon, Chastopteris, Clado- 



stephus, etc.). 

 Order 4. Eucceliaceae ; including the families, 



Mesogloeeae (Chordaria, Mesogloea, Castagnea, etc.). 



Sporochneas (Sporochnus, Carpomitra). 



Striarieas (Striaria, Stictyosiphon, etc.). 



Stilophoreae (Stilophora). 



Dictyosiphoneae (Dictyosiphon, etc.). 



Scytosiphoneae (Scytosiphon, Colpomenia, Phyllitis, Afapero- 



coccus.) 



Punctarieae (Punctaria, etc.). 



Order 5. Laininariaceaa (Laminaria, Alaria, Chorda, etc.). 

 Order 6. Cutleriaceae (Cutleria, Zanardinia). 



Series (b) Phaeogamae : sexual reproduction oogamous; asexual, wanting, 



or by non-motile spores : no gonidia. 

 Order 7. Tilopteridaceae. 

 Order 8. Dictyotaceae. 

 Order 9. Fucaceae. 



Order 1. Syngeneticae. Body unicellular, the cells being held together by 

 mucilage, forming a colony. Eeproduction by division, and by asexually pro- 

 duced spores. 



This order includes two genera, Hydrurus and Chromophyton ; in the former 

 the colony consists of many cells and is attached, in the latter it consists of 

 ei^ht cells and is unattached. 



In Hydrurus, each cell is an ellipsoidal mass of protoplasm, enclosing a 

 nucleus, one or two contractile vacuoles, and one or two chromatophores in the 

 form of a plate or ribbon each containing a pyrenoid. The cells multiply by 

 division. Asexual reproduction is effected by means of zoospores, formed by 

 division of a cell into two or four, which are set free by the disorganisation of 

 the investing mucilage and move by means of a single cilium ; these come to 

 rest, and each gives rise by division to a new colony. Also by means of rest- 

 ing-spores formed one from each vegetative cell. 



v. s. B. S 



