840 



XXXI. LEMNACE^. 



Grantia microscopies, 

 Plant, entire and cut vertically (mag.). 



Orantia. 

 Seed cut vertically (mag.). 



Telmatophaee. 

 Fruit laid open 

 (mag.). 



Telmatophaee. 

 Embryo 

 (mag.). 



Telmalophace. 

 Seed, entire and cut vertically (mag.). 





Wolffia 



brasitientis. 



Entire plant 



(natural 



size). 



Wolffla. 



a. anther; 6. pistil; c. shoot; 

 <'. cavity containing the shoot (mag.). 



Wolffla. 



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 trachea?, transient in the pistil, sometimes apparent throughout the tissue 

 of the plant (Spirodela) ; lower surface of the fronds usually bearing at the middle 

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

 duced to one (Lemna, Grantia, Telmatophaee); sometimes with no rootlets (Wolffia). 

 INFLORESCENCE imbedded in the frond. FLOWERS 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. OVARY 1 -celled, 1 many-ovuled ; ovule anatropous (Spirodela, Telmato- 

 phaee), or semi-anatropous (Lemna), or orthotropous (Wolffia). FRUIT 1-many- 

 seeded, indehiscent (Lemna, Wolffia), or dehiscing transversely (Telmatophaee). 

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

 tegium at the inicropylar point ; albumen fleshy or scanty. EMBRYO axile, straight ; 

 radicle superior, inferior or vague. 



Lemna. 



PRINCIPAL GENERA. 

 Telmatophaee. Spirodela. Grantin. 



Wolffia. 



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

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

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



