HYDROCHARDIELE 559 



HYDROCHARIDE^. 1 



Benth. et Hook. Gen. PI. iii. 448. 



Fruit and Seed. The ovary is inferior, one-celled, with 

 three to six placentas, rarely fewer or more, parietal or pro- 

 jecting into the centre of the cavity without uniting ; ovules 

 several on each placenta, pendulous or, especially the lower 

 ones, ascending, anatropous or sometimes orthotropous. 

 The fruit is submerged, globose, ovoid, oblong or linear, 

 dry or more or less pulpy, bursting irregularly through swelling 

 of the jelly-like contents, or opening by decay of the pericarp ; 

 one- or six- to many-celled by coalescence of the placentas 

 in the centre ; pericarp membranous or rarely somewhat 

 fleshy. The seeds are numerous, oblong ; the outer layer of the 

 seed-coat consists of spirally thickened cells, swelling up and 

 becoming mucilaginous in water ; the inner layer is usually 

 hard and more or less crustaceous, as in Stratiotes, and 

 especially in Blyxa, where it is sculptured and almost bony. 

 In some species, as B. echinosperma, the testa has thorny pro- 

 longations. The seeds are small in the Vallisnerieae, Blyxa 

 and the Otteliea^, larger in the other tribes. They are ex- 

 albuminous, the embryo completely filling the seed. 



In the freshwater genera the hypocotyl coheres with the 

 cotyledon into a more or less oval mass, including the small 

 plumule at the base of a lateral cleft. As examples, compare 

 Lagarosiphon muscoides, figured by Caspary, 2 who says ' the 

 embryo has a very strong resemblance to that of Naias major, 

 minor, and flexilis, and gives an indication of the systematic 

 position of the Hydrillese.' Vallisneria, Ottelia, and Hydro- 

 charis also follow this type. The embryo terminates in a 

 small radicle. 



Stratiotes is exceptional among the freshwater genera. 

 Here 3 the cotyledon is distinct from the hypocotyl, linear - 



1 In this and some of the following Orders I have no observations to record. 

 It may still, however, he convenient, for purposes of reference, to give a short 

 description of the fruit and seed. 



2 Die Hydrillen, in Pringsh. Jahrb. i. 478. 



3 Irmisch, Flora, 1865, p. 81, t. 1. 



