THE ANGIOSPERMAE 1265 



corolla of luminous white colour and five exserted anthers, at the same time 

 diffusing a rich scent. It is pollinated by a moth, Dianthoecia albimacida, 

 the males of which come for nectar. The females, however, lay eggs in the 

 ovary of the flower and the larvae consume some of the ovules, though the 

 remainder mature normally. The insects can only come flying, as the plant 

 is covered with sticky hairs, and as the stamens ripen some time before the 

 carpels, cross-pollination is ensured, for the stigmas alone are exposed on the 

 third night of opening. 



A species of Orchid from Madagascar, Angraeciim sesquipedale, has a 

 spur which reaches a length of nearly 30 cms., the longest known. It is 

 supposed to depend for pollination on some species of moth with a pro- 

 boscis long enough to reach the stored nectar. No such insect is known, 

 though some Sphinx moths in Brazil have probosces over 15 cms. long. 

 There may be here, also, a state of dependence between flower and insect, 

 though it has not been proved. The contrary suggestion has been made 

 that Angraecum is pollinated by small flies which creep bodily down the 

 spur. 



There are numerous night-flowering species, like Silene nutans, which 

 was referred to above. Several species of Nicotiana, Matthiola tristis, the 

 night-scented stock, and the night-flowering Cactus, Cereus nycticalus, are 

 all well-known plants in this category. Most of them have white or pale 

 yellow or lavender flowers, colours which have a luminous quality in dim 

 light and are easily picked out at night. Some species are also night-scented 

 and all are pollinated by night-flying insects, particularly moths. Some 

 observers have remarked that flowers of bright red and orange-red shades, 

 which are normally invisible at night, shine with intermittent phosphores- 

 cence, like some of the wood-destroying Fungi. This has been called the 

 Elizabeth Linnaeus Phenomenon, after the sister of Linnaeus, who first 

 noticed it in a garden bed filled with Tropaeohim speciosiim. Another plant 

 supposedly phosphorescent is Lychnis chakedonica, whose flowers are one 

 of the brightest reds in nature. The luminosity comes and goes in periods 

 of a few seconds, is greatest during dewfall and fades later in the night. 

 There is, however, a strong suspicion that the effect is only an illusion 

 of the eye. 



Some night-flowers only last for one night, as in the Cereus mentioned, 

 which is common in many tropical parts of America and the Pacific islands, 

 where it is called " Queen of the Night". Other species may open succes- 

 sively for several nights, as in Silene nutans, the flower being closed to visitors 

 during the day, by the incurling of the petals, so that the flower resembles an 

 unopened bud. 



Many flowers which have an unusually short life, opening only for a few 

 hours, whether by night or by day, have the further peculiarity that the 

 petals, on withering, become crumpled and pulpy, their cell-sap exuding 

 to the surface. The petals in this condition are visited by flies which suck 

 up the exuded sap and at the same time cover themselves with pollen from 

 the anthers, which they convey to other flowers. The flowers of the im- 



