•80 



DICOTYLEDONS 



and extend beyond its branches. This enables it to get water 

 from a greater space than most plants of its size can. 



The Stem ol Vinca does not grow high, but has numerous 

 long branches, the tips of which only are erect. Small plants, 

 like Vinca, generally have a herbaceous stem which does not last 

 for more than one season. Vinca has a strong woody stem, in 

 which it can store up food stuff and moisture for the time of need. 

 This stem, moreover, is covered with a very tough and leathery 

 hark which will not easily allow the moisture contained in its 

 inner layers to evaporate. The sap in the stem is, besides, slimy, 



and slimy fluids, as a matter of fact, 

 dry up very slowly (compare Cactus, 

 page 58). 



The elliptic Leaves of Vinca are 

 placed opposite. They are shiny 

 above and provided with a thick 

 epidermis, which conditions reduce 

 the evaporation (see Mango, p. 25). 

 Touch the leaves and you will see 

 that, though they shine and appear 

 glabrous or smooth, there is a tine 

 coat of down all round the epider- 

 mis. This also helps to reduce the 

 evaporation. 



2. The Flowers grow in pairs in 



Horal tube are removed to show tlie the axils of the IcaVGS. The CalyX is 

 stamens a.Ml the style. On the left ^'^^'^^^^ ^^^^0 tlve filiform Segments, 

 side: the upper part of the style ,„, ,, • , o ^ ^^ 



.,, , , , ,., ,. ' The corolla consists of a long cylin- 



with the hourglass-like stigma. ^ ^ 



drical tube spreading at its upper end 

 into five broad limbs, which are contorted in bud, but are at right 

 angles to the tube (salver-shapecl) when open. The mouth of the 

 tube, tinged with dark crimson, is slightly raised, surrounded by 

 a corona of hairs, and very narrow. But a little below, the tube 

 widens, making room tor live sessile stamens, which form a cone 

 under whicli tlic liourglass-like stigma of the h)ng and slender 

 style is situated. Tlie latter rises from the combined tip of two 

 iipocarpous seed-vessels at the bottom of the tloral tu])e (fig. 80). 



Fig. 80.— Flower of Vinca. 

 The two front lobes and half of the 



