466 A TEXT-BOOK OF BOTANY. 



IT. ORDER NAIADALES. 



This order, as with other rather primitive orders, is made up 

 mostly of aquatic and marsh plants, the flowers frequently being 

 spicated. 



The NAiADACEvE or Pond-weed family comprises such genera 

 as Potamogeton, the common Pond-weed, and Zostera, or Eel- 

 grass, which is extremely common in bays and estuaries in all 

 parts of the country, and in many places its collection forms an 

 active industry. It is used in upholstery work and as a packing 

 material. 



To the ALiSMACE^ or Water-Plantain family belong Alisma, 

 the Water-Plantain, and Sagittaria, or Arrow-head, which is a very 

 attractive plant (Fig. 253) . Of the latter there are a large number 

 of species which are widely distributed. 



III. ORDER GRAMINALES OR GLUMIFLOR^. 



This order is composed of the two families, grasses (Gram- 

 inese) and sedges (Cyperaceae). 



a. GRAMINE^ OR GRASS FAMILY.— The plants of this 

 family are nearly all herbs having cylindric, generally hollow 

 culms with swollen nodes. The leaves are exactly alternate, and 

 have long sheaths which are split or seldom closed, tubular, and 

 nearly always with a distinct ligule. The flowers are mostly 

 hermaphrodite and borne in spikelets with alternate floral-leaves, 

 the spikelets themselves being borne in spicate or paniculate in- 

 florescences. Each spikelet (Figs. 255, 256) consists of two 

 (seldom more) empty glumes, which are the lowest floral-leaves 

 in each spikelet ; a varied number of flowering glumes, frequently 

 awned or toothed, are situated inside the empty glumes, and 

 ea-ch of which subtends a short branch (the rhachilla), the latter 

 bearing an adorsed fore leaf (the pale), which is generally two- 

 keeled and two-toothed, enclosing two minute scales (lodicules) 

 and the flower. The flower has mostly three stamens (there 

 being six stamens in Oryza and Bambusa), with the anthers versa- 

 tile, and a simple gynsecium consisting of one carpel having two 

 styles and a plumose stigma. The ovary is unilocular with one 

 ascending or pendulous ovule. The fruit is a grain or caryopsis. 



