84 



DICOTYLEDONS 



a very strong and useful fibre. The soft, white, woolly tomentum 

 on the stem and on the underside of the leaves affords the plant 

 protection against the withering intiuence of dry winds. Owing 

 to this and the thickness of the epidermis, the plant is, in spite 

 of the size of its leaves, in a position to remain green even 

 during the hottest and driest part of the year. Leaves pretty 

 large, opposite, oblong-obovate with auricled base and short stalks. 

 2. The Flowers grow in large cymose umbels. Sepals five. 

 Corolla bluish, five-lobed, bell-shaped; lobes valvate in bud. 

 Of peculiar interest is the structure of the essential or reproduc- 

 tive organs of this flower. What strikes us first when we examine 

 it, are five large, wax-like, bluish bodies, curiously recurved, 

 alternating with the corolla lobes and radiating from the stami- 

 nal column (fig. 82, 3). These appendages form what is called 

 the corona. If we remove them carefully, we shall find in the 

 cavity two seed-vessels with a style each. These, however, are 

 united at the top and support a five-rayed, fiat stigma (fig 82, 4). 

 At each corner of this cake-like stigma a wiry, brown body can 

 be seen, to which two club-shaped pollen-masses are attached, 

 each of them belonging to two distinct anthers. This is evidently 

 a contrivance for cross-fertilization by the agency of insects 

 (compare Orchids). Insects that alight on the broad stigma of 

 the style in search of nectar detach some of the pollen-masses 



with their feet, and 

 carry them to an- 

 other flower, which 

 is thus pollinated. 



3. The Fruit is 

 made up of two large, 

 ovoid, dry follicles, 

 each splitting up in 

 one line (the inner 

 or ventral suture) 

 and containing numerous fiat seeds packed together in beautiful 

 order. One of the two follicles is sometimes absent by abortion. 

 Each seed is crowned with silky hair. When ripe, the feather 

 expands like an umbrella, and caught by the wind, may be 



Fif^. 83. — Follicle of Calolropis <ji(jantea. 



