840 



XXXI. LEMISTACB^. 



Qrantia microscopica. 

 Plant, entire and cut vertically (mag.)* 



Grantia. 

 I cut vertically (mag,)- 



Telmatophace. 

 Fruit laid open 

 (mag.). 



^- 



TelmatopTiace, 

 . entire and cut vertically (mag.). 



Wolffia 



hi'asiliends. 



Entire plant 



(natural 



size). 



" "Wolfia. 

 a. antller ; h, pistil ; c. shoot ; 

 (/. cavity containing the shoot (mag.). 



Wolffia. 

 a. point of union of 

 frond; 6. opening for 

 exit of shoot (mag.). 



Herbaceous plants, very small, floating freely on the surface of stagnant water, 

 stemless and reduced either to lenticular or obovate disks {fronds), flattened above, 

 sometimes more or less convex below ; or to membranous productions springing at 

 right angles to each other ; fronds emitting by 2 lateral slits, or sometimes by 1 

 basilar slit {Wolffia) young fronds similar to the first, with no vessels, or with rudi- 

 mentary tracheae, transient in the pistil, sometimes apparent throughout the tissue 

 of the plant {Spirodela) ; lower smface of the fronds usually bearing at the middle 

 rootlets terminated by a membranous cap (pileorrhiza), fascicled {Spirodela), or re- 

 duced to one {Iiemna, Grantia, Telmatophace); sometimes with no rootlets {Wolffia). 

 Infloeesoenoe imbedded in the frond. Flowees achlamydeous, naked, or enclosed 

 in a spathe, reduced to 1-2 stamens, accompanied by a sessile pistil"; spathe urceolate, 

 membranous, bursting irregularly by the evolution of the stamens ; filaments filiform ; 

 anthers with 2 sub-globose cells, opening by a transverse slit ; pollen muricate, 

 opening by a single slit ; style continuous with the top of the ovary ; stigma infundi- 

 buliform. Otabt 1 -celled, 1— many-ovuled ; ovulp anatropous {Spirodela, Telmato- 

 phace), or semi-anatropous {Lemma), or orthotropous {Wolffia). Feuit 1-many- 

 seeded, indehiscent {Lemna, Wolffia), or dehiscing transversely (Telmatophace). 

 Seed with coriaceous corky fleshy testa, endopleura membranous, forming an embryo- 

 tegium at the micropylar point; albumen fleshy or scanty. Embeto asile, straight ; 

 radicle superior, inferior or vague. 



Lemna. 



PRINCIPAL GENEEA. 

 Telmatophace. Spirodela. Grantia. 



Wolffia, 



At tlie beginning of winter Lemnas sink into the mud, where they perhaps all undergo trnnsforma- 

 tions analogous to those exhibited by X. triscula, the sterile membranous portions of which give rise to 

 an orbicular fertile plant, which is similar in all points to X. minor. 



