LYTHRARIEAE 



435 



Thymifolia Z. (homomorphous according to Koehne), and twenty other species of 

 the same genus, as well as some belonging to the genera Pemphis, Rotala, and 

 Nesaea. (Cf. Vol. I, p. 491.) Numerous species are homomorphous, among which 

 Koehne enumerates no fewer than 340 belonging to Ly thrum, including our native 

 species L. Hyssopifolia Z. 



Koehne gives the following particulars in his newest monograph of the order 

 (' Lythraceae,' in Engler u. Prantl, d. nat. Pflanzenfam., Ill, 7, pp. 4-5). Eight 

 species exhibit trimorphous heterostyly (Lythrum maculatum Kjcersk., L. flexuosum 

 Lag., L. virgatum Z., L. Salicaria Z., Nesaea Kilimandscharica Koehne (?), N. 

 Schinzii Koehne, N. sagittifolia (Sond.) Koehne, Decodon verticillatum (L.) Ell.) and 

 possess two whorls of stamens. Dimorphous heterostyly obtains in five species 

 possessing two staminal whorls (Lythrum rotundifolium Hochst., Pemphis acidula 

 For st., Nesaea rigidula (Sond.) Koehne, N. mucronata Koehne, N. Volkensii Koehne). 



Fig. 147. Lythrum Salicaria, L. (after Herm. Muller). (i) Long-styled flower, after removal of one- 

 third of the calyx, corolla, and stamens ; seen from above. (Pollen green.) (2) Medium-styled flower, 

 ditto. (Pollen yellow.) (3) Short-styled flower, ditto. (Pollen yellow.) (4) Medium-styled flower, seen 

 obliquely from the right front, a, long style or stamens; b, medium style or stamens; c, short style or 

 stamens ; </, nectar. 



The following fourteen species possessing but one whorl of stamens are dimor- 

 phously heterostylous (Rotala myriophylloides Welw., R. floribunda (night) Koehne, 

 R. nummularia Welw., Lythrum lineare Z., L. album H.B. and K, L. ovalifolium 

 (Engelm.) Koehne, L. acinifolium (DC.) Koehne, L. gracile Benth., L. lanceolatum Z., 

 L. californicum S. Wats., L. alatum Pursh, L. Vulneraria Ail., Nesaea lythroides 

 Welw., N. Woodii Koehne). About 6 % of the 450 species included in the order 

 are heterostylous. The most specialized forms as regards pollination are the strongly 

 zygomorphous flowers of species of Cuphea and Pleurophora. 



Some species bear cleistogamous or pseudo-cleistogamous flowers. Ammannia 

 latifolia Z., for instance, is often cleistogamous, according to Koehne. Treviranus 

 states that the following are self-pollinated before their flowers open : Cuphea 

 silenoides Nees, C. floribunda Lelm., and C. Melvilla Lindl. (Bot. Ztg., Leipzig, xxi, 

 1863). 



296. Lythrum L. 



Flowers red, trimorphous, dimorphous, or homomorphous; with concealed 

 nectar, secreted at the bottom of the tubular receptacle. 



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