GROUP IV. — PHANEROGAMIA : ANGIOSPERMJ: : MONOCOTYLEDONES. 553 



Sub-Class III. PETALOIDE^. 



Flowers ambisporangiate, rarelj monosporangiate ; perianth 

 rarely wanting, usually biseriate, the corolla usually petaloid, and 

 sometimes the calyx also. 



SERIES I. HYPOGYNJi:. 



Ovary superior. 



Sub-series. Apocarpce. 



Gynaeceum more or less completely apocarpous. 



Cohort 1. Alismales. Marsh- or water-plants ; flowers fre- 

 quently monosporangiate ; seeds without endosperm. 



Order 1 . Naiadace^. Perianth 0, or of 2-4 segments ; stamens 

 1-4 : ovaries 1-4, with usually a single erect or suspended ovule. 

 Water-plants. 



Fam. 1. Naiadea. Flowers monosporangiate. 



In the genius Naias the flowers are solitary or in spikes, and are dioecious : 

 perianth of one or two gamophyllous series : S flowers with 1 stamen, ? flowers 

 with 1 carpel : ovule erect. N. flexilis is the only British species. 



Fam. 2. Zostcrea. Flowers monosporangiate. 



In Zostera, the Grass-wrack, the flowers are monoecious, and without a 

 perianth ; they are borne in two rows on one side of a flattened spike ; stamen 

 1, carpel 1. Zostera marina and nana are the British species living in the 

 brackish water of estuaries. Phyllospadix, a North American (west-coast) genus, 

 also belongs to this family : it is dioecious. 



Fam. 3. Zaniiichelliece. Flowers monosporangiate. 



In Zannichellia, the Horned Pondweed, the monosporangiate flowers are 

 monacious, and are solitary or in spikes : S flower, perianth 0, stamen 1 ; ^ 

 flower, perianth bell-shaped, carpels 4-6. Z.palmtris is the only British species. 

 Altheuia, the other genus, is sometimes dioecious. 



Fam. 4. Gijmodocece. Marine. Flowers monosporangiate, dioecious : perianth 

 : (J flower consists of two connate stamens ; ? flower of two adjacent mono- 

 merous ovaries, each bearing a style which branches into two stigmata ; ovule 

 single, suspended, orthotropous. 



To this family belongs the genus Cymodocea (with the sub-genera Phu- 

 cagrostis, Physoschoenus, and Amphibolis) ; widely distributed on tropical and 

 sub-tropical sea-coasts. 



Fam. 5. Posid'miea. Marine. Flowers monosporangiate, sometimes ^ , in 

 cylindrical compound spikes, the upper flowers of which are ^ : perianth : the 

 S flower consists of 3 stamens, the ? flower of a single carpel. 



To this family belongs the single geous Posidonia ; P. oceanica inhabits the 

 shores of the Mediterranean. P. anstralis the shores of temperate Australia. In 

 Zostera, Posidonia, and Cymodocea, the pollen is filiform or confervoid (see p. 520). 



Fam. 6. Potainogetonece, Flowers $ . 



