HARDWICKE'S SCIENCE-GOSSIP. 



i8i 



course characteristic of wind-fertilized flowers and so 

 far everything seems to favour the anemophilous 

 theory ; but how is it with the pistillate flower ? The 

 fertile plants are easily distinguished from the male 

 by the absence of the long green spikes, and might 

 easily be passed over as flowerless, especially in the 

 earlier stages, when the flowers are almost concealed 

 amongst the upper leaves, except perhaps one or two 

 that contrive to push out their heads, as if waiting for 

 any chance pollen that the wind might bring to them. 

 If one of the tiny inflorescences be picked it will be 

 found to be growing in the axil of a leaf whose lower 

 portion is very closely rolled inwards, the tip only 

 being fully expanded. Might not these be favourable 



Fig. 169. — 3. Drop of Honey, i. Pistillate Flower (Mag.) 



to the access of wind-borne pollen to the flowers ? 

 There are as a rule two flowers to each raceme, and it 

 s curious that the 'only bract belongs to the lower 

 flower, it being invariably absent from the upper one 

 in plants that have come under the writer's observa- 

 tion. The upper flower is the first to open ; it has 

 three sepals, one of which is removed in the drawing 

 that the essential organs may be more clearly seen ; 

 but when the perianth first opens, the flower is in 

 the condition shown in the above figure (2), very 

 quickly the large stigmas expand and spread out their 

 sticky crinkled surfaces to receive the pollen, and it 

 will be seen that the fertile flower of Mercurialis con- 

 sists principally of th; pistil with its enormously 



developed stigmas. The ovary is two-celled and 

 even in a very young state it is not difficult to remove 

 the outer portion and find that one solitary ovale 

 fills each cell, that it is suspended from the placenta, 

 and if cut through lengthwise the pear-shaped embr/o 

 may also be discerned lying with its broad cotyledons 

 in the albumen, the radicle pointing obliquely up- 

 wards. To return again to our flower. The two 

 stamens have not yet been examined ; they may be 

 seen on each side of the ovary seated on two elon- 

 gated glands that alternate with the carpels and form, 

 the disk. The filaments have no anthers, for the 

 little knob at the top of the nearest must not be mis- 

 taken for one. It is intended to represent the drop ot 

 honey that is frequently if not always to be seen 

 exuding from the tip. That it is really honey one 

 may easily prove by tasting it, though at first sight it 

 might be taken for a simple drop of moisture. That 

 honey should be secreted by these two otherwise 

 useless stamens is interesting both as an example of 

 the way in which organs may be made to subserve 

 other purposes than those for which they were 

 originally intended, and also because honey is always 

 secreted for the special purpose of attracting insects. 

 See how this improvised nectary lifts its tempting 

 sweets above the recurved pistil, as though well 

 aware that such an insignificant little green flower 

 would never be suspected of containing any thing so 

 delicious and must needs hold out its cup of nectar to 

 passers-by and demand their attention ! The stami- 

 nate flowers of course secrete no honey, but their 

 abundant pollen is sufficient to ensure insect visitors. 

 What must we say then of Mercurialis ? The long 

 pendulous stamens, the light abundant pollen, and 

 the large stigmas, all point to the conclusion that 

 the plant is adapted exclusively for wind fertilization, 

 while the drops of honey on the two abortive 

 stamens seem to bid us not be too sure that this is 

 correct. The fertile flowers of Mercurialis open in 

 succession, and as the staminate flowers do likewise 

 there is always some pollen to be carried to them by 

 one agency or the other ; indeed it is remarkable how 

 few staminate flowers are open at one time, as if the 

 plants must needs husband their resources and not 

 expend them all at once with too lavish prodigality. 

 Mercurialis is said to have been named by the 

 Romans in honour of their god Mercury, following 

 the example of the Greeks, who called it the "plant 

 of Hermes," but whether because he was the dis- 

 coverer of the plant or of its supposed poisonous 

 properties is not clear. Our popular name of dog's 

 mercury is supposed to announce its inferior worth, 

 as in the case of the dog violet and dog rose. The 

 plant assumes in drying a curious blue tinge, which is 

 said to indicate the presence of indigo, and a German 

 botanist has detected two colouring substances in thfi 

 root, one blue, the other carmine. 



M. D. D. 



Hawks head, Ambleside. 



