NYSSACEAE 851 



and 4 or rarely 8 stamens : fruit globose-ovoid, 2 mm. long, each carpel strongly 2-keeled 

 on the back and roughened. [M. scabratum Michx.] 



In shallow ponds and ditches, Rhode Island to Missouri, Florida, Texas and Mexico. Also in 

 Central America. Spring and summer. 



4. Myriophyllum heterophyllum Michx. Normally stout, 2-10 dm. long. Leaves 

 of 2 kinds, the submersed ones crowded, more or less scattered, 1.5-5 cm. long, the hair- 

 like segments in 6-10 pairs, the emersed leaves in whorls of 3's to 6's, linear to oblong, 

 sometimes varying to lanceolate or oblanceolate, sharply serrate : spikes erect or slightly 

 nodding, 1-5 dm. long, simple or branched : flowers snorter than the bracts, the staminate 

 about 3 mm. broad, with 4 oblong or ovate-oblong petals and 4-6 stamens : fruit 2-2.5 mm. 

 long, each carpel 2-keeled on the back and slightly roughened. 



In ponds and slow-running water, Quebec to Minnesota, Florida, Texas and Mexico. Summer. 



Order 27. AMMIALES. 



Herbs, shrubs, trees or vines. Leaves alternate or opposite : blades mostly 

 toothed, lobed, divided or compound. Flowers perfect, polygamous or dioecious, 

 variously clustered, but commonly in umbels. Hypanthium present. Calyx of 

 typically 5 relatively small sepals surmounting the hypanthium. Corolla typ- 

 ically of 5 petals. Androecium of as many stamens as there are sepals or petals. 

 Gynoecium of 2 united carpels or rarely more, or sometimes 1-carpellary. Ovary 

 inferior, 1 -several-celled, sometimes surmounted by a stylopodium. Stigmas ter- 

 minal or introrse. Fruit drupaceous or baccate, or dry and a cremocarp with 

 smooth or spiny, ribbed or winged carpels. 



Fruit drupaceous or baccate : gynoecium 1-several-carpellary, if 2-carpellary, stigmas introrse. 

 Ovule with a dorsal raphe : leaves mostly opposite ; blades entire or merely toothed. 



Fam. l. NYSSACEAE. 



Ovule with a ventral raphe : leaves mostly alternate ; blades lobed or com- 

 pound. Fam. 2. HEDERACEAE. 

 Fruit dry, a cremocarp : gynoecium 2-carpellary : stigmas terminal. Fam. 3. AMMIACEAE. 



FAMILY 1. NYSSACEAE Dumort. DOGWOOD FAMILY. 



Shrubs or trees, or rarely herbaceous shrubs. Leaves alternate or opposite, 

 without stipules : blades mostly firm or leathery, usually entire. Flowers perfect 

 or unisexual, in cymes or heads, sometimes subtended by involucres. Calyx of 

 mostly 4-5 sepals. Corolla of 4-5 or rarely many, imbricated or valvate petals, 

 inserted at the base of an epigynous disk, or wanting. Androecium of usually 

 as many stamens as there are petals and inserted with them. Filaments terete 

 or flattened. Anthers attached at the base or the back. Gynoecium of 1-4 

 united carpels. Ovary 1-4-celled, inferior. Styles united. Stigmas entire, lobed 

 or cleft. Ovules solitary in each cavity or rarely 2, anatropous, pendulous. 

 Fruit mostly a drupe, with an acid pulp, stones solitary or rarely 2, 1-4-celled. 

 Seed with a membranous or thin-leathery testa. Endosperm fleshy. [Cornaceae 

 Link.] 



Flowers dioecious or polygamo-dioecious : stigmas lateral. 



Stigmas 2 : ovules 2 in each cavity : staminate flowers in ament-like spikes. 1. GARRY A. 



Stigma 1 : ovule 1 in each cavity : staminate flowers capitate. 2. NYSSA. 



Flowers perfect: stigmas terminal. 



Flowers in open cymes, not subtended by an involucre : fruit surmounted by the 



style. 3. SviDA. 1 



Flowers in a head subtended by a large involucre : fruit surmounted by the calyx. 4. CYNOXYLON.* 



1. GARRY A Dougl. 



Shrubs, with 4-angled branches. Leaves opposite, persistent : blades entire or slightly 

 toothed. Flowers dioecious, inconspicuous, in axillary ament-like spikes, the staminate 

 with 4 narrow sepals, no petals, 4 stamens with distinct filaments and linear anthers, and an 

 obsolete gynoecium. Pistillate flowers with 2 more or less manifest sepals and a gynoe- 

 cium with a 1-celled ovary, 2 stigmas and 2 pendulous ovules. Drupe short, terminating 

 *n the 2 persistent stigmas. Seeds 2, or sometimes 1, flattened. 



1 The genera Svida and Cynoxylon are commonly included in the genus Cornus. 



