262 Excerpta Botanica. 



I first collected L. minor in flower and fruit at Berlin in 1835, 

 and since that time I have each year detected it again in the same 

 state whenever I searched with care. 



2. L. trisulca, Linn. Frondes lanceolatse, apice repando-dentatse, 

 tenues, in stipitem elongatum persistentem attenuate, ideoque 

 multifariam aggregate, exclusis floriferis submersse. Stauroge- 

 ton, Reich. L. intermedia, Ruthe. L. cruciata, Roxb. 

 In 1836 I found L. trisulca in flower, and have since regularly 

 detected the flowers wherever I encountered this species. The 

 reason why this species has been so rarely found in flower, is that 

 the search has been made at too late a period, as it generally flowers 

 abundantly in April and the beginning of May. The flowers will 

 be seen on those plants which are submerged near the surface; 

 after flowering they multiply themselves laterally and are then sub- 

 merged. 



III. Thelmatophace. 

 Spadix brevissimus, sed discernendus. Flores masculi duo. Fila- 

 menta recurva, medio dilatata ; ovarium uniloculare, bi-multi- 

 ovulatum, ovulis erectis anatropis ; stylus elongatus, recurvus ; 

 fructus : capsula membranacea, dehiscentia circumscissa, di- 

 polysperma ; semina erecta ; albumen paucissimum ; embryo 

 ovatus ; plumula maxima ; radicula infera. 



1. T. gibba. Frondes obovatse vel suborbiculata?, adultse inferne 

 vesiculoso-convexse ; stipite frondis novelise discreto, fragillimo, 

 ideoque frondibus adultis subsolitariis. Lemna gibba, Linn. 



/3. trichorhiza, fronde superne rubente, radice longissima. Lemna 

 trichorhiza, Thuill. 



In 1837 I first observed T. gibba in flower, and since frequently. 

 It is the rarest species at Berlin. 



ft Vasis spiralibus in tola planta conspicuis ; fronde novella stipidis binis 

 (inferiori et superiori) membranaceis aucta, polyrhiza. 



IV. Spirodela. 

 Flores masculi duo ; filamentis inferne angustatis. Flores foeminei. 



Ovarium biovulatum, ovulis erectis anatropis ; stylus ; 



stigma ; fructus 



1. S. polyrhiza. Frons planiuscula, nervis palmatis, polymorpha, 



orbiculari-ovata ; apice obtuso vel acuto. Lemna polyrhiza, 



Linn. L. bannatica, Kit. L. orbicularis, Kit. L. thermalis, P. 



Beauv. L. orbiculata, Roxb. 



Notwithstanding the most careful search I did not detect S. 



polyrhiza in flower until 1839, when I found at Werningerode the 



male flowers, or those in which the pistil is imperfectly developed. 



The only previous notice of the flowers of this species is in Wiggers 



Prim. Fl. Holsat. 



Appendix. 

 Lemna arhiza, Mich, according to the observations of Hoffmann 

 is a good species, but, as the flowers and fruit are still wanting, 



