GENTIANEAE 



97 



Hh: Gentiana punctata Z., G. acaulis Z., G. asclepiadea L., G. ciliata Z., 

 G. purpurea Z., G. Amarella Z. ; 



HhL : Gentiana tenella Roii., G. nana Wul/., G. campestris L., G. obtusifolia 

 Willd., G. aurea Z. ; 



Lb : Gentiana nivalis Z. ; 



Lbdh-m (dh-m= diurnal hawk-moths) : Gentiana vema Z., G. bavarica Z. 



578. Menyanthes Tourn. 



Flowers mostly dimorphous, with concealed nectar secreted at the base of the 

 ovary. 



1888. M. trifoliata L. (Sprengel, 'Entd. Geh.,' pp. 102-3; Warming, 

 ' Bestovningsmaade/ pp. 13-15; Heinsius, Bot. Jaarb. Dodonaea, Ghent, iv, 

 1892, p. 71; MacLeod, op. cit., v, 1893, p. 383; Kemer, 'Nat. Hist. PI.,' 

 Eng. Ed. I, II, pp. 310-n; Warnstorf, Verb. bot. Ver., Berlin, xxxviii, 1896; 

 Knuth, 'Bl. u. Insekt. a. d. nordfr. Ins.,' pp. 104-5.) The flesh-coloured flowers 

 of this species are arranged in racemes, and are remarkable on account of the 



Fig. 258. MenyantJus trifoliata^ L. (from nature), (i) Short-styled flower, after removal of a petal 

 and a stamen (natural size). (2) Long-styled do. (natural size). (3) Stigmatic papillae of long style 



(X 4). (4) Do. of short style (X 4). (5) Pollen-grain of a long stamen (x 70). (6) Da of a short 

 stamen (x 70). 



fringed limbs of the petals. These not only enhance conspicuousness, but protect 

 the nectar against rain and unbidden guests. Only the long-styled form was seen 

 and depicted by Sprengel. The plant is not heterostylous everywhere, for Warming 

 describes it as homostylous in West Greenland, between 6i and 69 N. lat. The 

 anthers and stigma are at the same level, or the latter a little higher. Automatic 

 self-pollination is therefore easily possible. {Cf. Fig. 259.) 



Warnstorf found the long-styled form at Ruppin, with stamens of the same 

 length, when the flowers opened, so that stigma and anthers were at the same level, 

 thus facilitating autogamy. The pollen is of a beautiful orange-yellow colour in 

 bulk: the individual grains are spheroidal to ovoid, and marked with closely 

 approximated, very delicate streaks, parallel to a large extent, and gradually dis- 

 appearing towards the poles. Curiously enough the cell-walls of the hairs on the 

 inner surface of the limbs of the petals exhibit similar, but feebler streaks. Heinsius 

 has measured the ovoid pollen-grains. Those of the long-styled form are on the 



