APOCARPEiE 375 



There is some appropriateness about the term 

 Naiadacese since all these plants are hygrophiloiis 

 and either aquatic or marsh plants, found in fresh or 

 salt water. 



Some one hundred and twenty species are known 

 included in sixteen genera. The group is related to 

 the last group. 



These plants are either herbaceous marsh plants 

 or, when aquatic, of the floating or submerged type. 

 The rootstock is creeping. The stems are long with 

 long internodes (or the plant may be stemless) , jointed, 

 branched, and slender. As a rule the leaves are 

 sheathing below, or have sheathing stipules within 

 the leaf-stalk sheath, and are alternate or opposite or 

 in two rows, floating. There may be no stipules. The 

 veins are parallel. 



The flowers are small, hermaphrodite (or the plant 

 may be monoecious), green, in the axils, solitary or in 

 spikes, arising from a sheathing bract. There is either 

 no perianth, or, if it is present, it is tubular or cup- 

 shaped, and consists of two to four scale-like segments, 

 inferior, valvate. There are one, two, four, or six 

 stamens which are hypogynous. The anthers are one- 

 to two-celled. The ovary is superior and consists of 

 one to four carpels, or of two, four, or six carpels, 

 with a single ovule in each carpel, erect or pendulous. 

 There is a single style and a separate or two to four 

 stigmas. The fruit consists of one, two, three, four, 

 or six utricles, achenes or drupes. They are one- 

 seeded. The seed is solitary. There is a membranous 



