432 



ANGIOSPERMAEDICO T YLEDONES 



XXXIX. ORDER HALORAGEAE R. Br. 

 (including Hippuridaceae Link, Gunneraceae Endl., and Callitrichaceae Link.) 



287. Myriophyllum L. 



Monoecious wind-pollinated water-plants. The anthers are versatile, and contain 

 abundant easily dispersed pollen. The stigmas are large, and very rough. Some 

 of the species are possibly water-pollinated. 



1021. M. verticillatum L. (Ludwig, Kosmos, Stuttgart, x, 1881-2, pp. 7-12.) 

 The small, greenish-yellow flowers of this species are arranged in spiked whorls 

 in the leaf-axils. They project above water, and are wind-pollinated. Ludwig states 

 that there are also submerged water-pollinated flowers. These, however, do not 

 appear to be universally distributed ; at any rate I did not observe them in the 

 island of Fohr. 



1022. M. spicatum L. (Ludwig, op. cit.) Ludwig says that the reddish 

 flowers of this species possess the same mechanism as those of M. verticillatum, 

 but submerged flowers have not been observed. According to Kerner, the female 

 flowers develop before the male ones. 



Only sterile plants of the species had been observed in Greenland, until 

 Vanhoffen discovered richly flowering specimens in a pond at Ikerusak (Abromeit, 

 ' Bot. Ergeb. von Drygalski's Gronlandsexped.,' pp. 11-12). As in Europe, the 

 stigmas of the female flowers were mature before the opening of the male ones. 



1023. M. alterniflorum DC. Here again only wind-pollinated flowers pro- 

 jecting above the water-level have so far been observed. 



288. Hippuris L. 



Water-plants with inconspicuous protogynous wind-pollinated flowers in the 

 leaf-axils. 



1024. H. vulgaris L. (Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 17 1-2.) 



In this species the part of the stem projecting 



^t _ from the water bears on each of its nodes (fifty 



Jr" S 1 Wj~ to sixty, or even more in number) a whorl of 



^f3_# // ten leaves. There is a small flower in the axil 



of each of these. At first the white, very papillose 



stigma projects 3 mm. beyond the ovary, while 



the sessile anther is still closed. When the 



stigma has withered a thin filament (i mr 



long) develops, and at its tip the dehiscec 



anther exposes its pollen to the wind. I ar 



unable to confirm Vaucher's assertion (' Hist. 



physiolog. des pi. d'Europe,' II, p. 362), that the 



oily yellow pollen is directly applied to the stigma. 



In Fohr, besides hermaphrodite stocks, I observed others that were purely 



female, or on which only some flowers possessed stamens. Kirchner also observed 



gynodioecism at Stuttgart ('Flora v. Stuttgart,' p. 419), as did Willis in F.nglanc 



(Proc. Phil. Soc, Cambridge, 1893). 



Fig. 146. Hippitrisvnlgaris, Z,.(from 

 nature, several times enlarged), (i) Flower 

 in the first (female) stage: a, sessile, 

 immature anther ; s, papillose stigma. 

 (2) Flower in the second (male) stage : 

 a, stalked dehisced anther; s, withered 

 stigma. 



