330 THE PLANT PHYLA 



(a) Sporophylls open, ovules and seeds 

 naked (gymnospermous). 



(1) Gametophytes dioecious; sperms cili- 

 ated and motile; sporophytes pro- 

 ducing microspores and megaspores 

 in spiral or whorled sporophylls, or 

 these aggregated into cones. 



Phylum 12. Cycadophyta. 



(2) Gametophytes dioecious; sperms not 

 ciliated, not motile; sporophytes 

 with sporophylls in cones. 



Phylum 13. Strobilophyta. 



v/ (b) Sporophylls closed, ovules and seeds 



covered (angios'permous). 



V (1) Gametophytes dioecious; sperms not 



ciliated, not motile; sporophytes 



with sporophylls in flowers. 



Phylum 14. Anthophyta. 



In the following systematic enumeration many of the families 

 are merely named in their sequence, without any characteriza- 

 tion or examples. Moreover the characterizations of all groups 

 are necessarily very brief and general. The examples cited are 

 of the more common genera, or those of particular interest to 

 the student. 



Phylum L MYXOPHYCEAE. The SUme Algae 



Usually blue-green, poorly developed cells, or filaments 



Class 1. AECHIPLASTIDEAE (Cyanophyceae). "Blue 

 Greens." Without nuclear mem- 

 brane. (Sp. about 2,000.) 

 Order Coccogonales. Green or greenish; unicellular. 

 Family 1. Chroococcaceae. Cells rounded. — Chroo- 



coccus, Gloeocapsa, Merismopedia. 

 Family 2. Chamaesiphonaceae. Cells elongated. — ■ 

 Chamaesiphon. 

 Order Hormogonales. Mostly green or greenish; fila- 

 mentous. 

 Family 3. Oscillatoriaceae. No heterocysts. — Oscil- 

 latoria, Lyngbya. 



