810 



XXII. NAIADES. 



Zoster a. 



Embryo ctit vertically, and portion of 

 cotyledon, showing the point. 



Zostera marina. 



Pistil laid open below to show the insertion of the 

 ovule (mag.). 



Zmtera. 



Frnit, entire and opened 

 (mag.). 



Zoi/tra. 



Embryo, entire and cut transversely 

 (mag.). 



sub- globular or ovoid; testa thin or membranous, smooth or reticulate. EMBRYO 

 macropodous. 



Zostera. 

 Ilalophila. 



Phucagrostis. 

 Posidonia. 



GENERA. 



Lemnopsis. 

 Najas. 



Phyllospadix. 



Catilinifl. 



Zostera inhabits the estuaries of the North Sea and Atlantic and Indian Oceans, Posidonia and Phvca- 

 fjrostis the Mediterranean, and TfiyUotpadix the -western shores of North America. CauKtria and Najax 

 inhabit fresh still waters in Europe and America. In Holland the leaves of Zostera are used in the con- 

 struction of dykes. For some years they have been used in France for stuffing mattresses and for packing. 



Adrien de Jussieu, -who studied the classification of Monocotyledons, divided them into albuminous 

 and exalbuuiinous, and the latter again into terrestrial (OrcJiidvet") and aquatic. The exalbuminous 

 aquatics have been divided into two sections, according to the presence or absence of a true perianth. 

 The chlamydeous section includes Alismacecp, Jltitome<F, and Hydrocharidcer, -which have six perianth 

 divisions, the three inner petaloid; the other fection comprises Jttncaffinea, Kaiadeer, Potamea; ard 

 Zosteracea>, which have a scaly, membranous, or herbaceous perianth, or are achlamydeous. The three 

 families of the first section are distinguished by free or coherent ovaries, and by the placentation ; those 

 of the second section by the embryo, which is brachypodous and homotropous in Jtmctrgiticee, macropodous 

 and antitropous in Zosteracea*, macropodous and amphitropous in Potamece, macropodous and homotropous 

 in Naiadete. 



With modifications we have adopted this classification, 1 and after many endeavours we have suc- 

 ceeded in uniting in what appear to us homogeneous groups, the exalbuminous aquatic Monocotylrdonous 

 genera, placed in one family by most botanists. Without overlooking the close affinity between Jvnca- 

 ginea, Potamece, Naiadetp, &c., we think that the form of the stigmas entire and peltate, or divided nnd 

 pointed may serve to group very naturally the different genera of Naiadea and Potamea, the latter being 



1 After many attempts by many botanists, it is 

 pretty clear that any linear arrangement of the Mono- 

 cotyledpnous families is quite impossible, and that there 

 is little .choice between several of them ; under which cir- 



stanees the simplest and most practical is that adopted 

 in this work. See Synopsis of Orders at the end. 

 En. 



