SECT. I 



MORPHOLOGY 



27 



assimilatory organs, but also serve as water-reservoirs in time of 

 drought. 



On the other hand a plant may lose its leaves more or less com- 

 pletely without any marked flattening or 

 thickening occurring in the stems, which 

 then take on a green colour ; this, for ex- 

 ample, is the case in the Broom (Spartium 

 scoparium), which-develops only a few quickly 

 falling leaves on its long, naked twigs. As 

 a rule, however, leafless green Phanerogams 

 will be found to have swollen stems, as in 

 the variously shaped species of Euphorbia 

 and Cactus. 



Reduction of the Shoot in Parasites. 

 A great reduction in the leaves, and also in 

 the stems, often occurs in phanerogamic 

 parasites, in consequence of their parasitic 

 mode of life. The leaves of the Dodder 

 (Cusciita, Fig. 202 b) are only represented 

 by very small yellowish scales, and the stem 

 is similarly yellow instead of green. The 

 green colour would, in fact, be superfluous, 

 as the Dodder does not produce its own 

 nourishment, but derives it from its host 

 plant. Cuscuta Trifolii, one of the most fre- 

 quent of these parasites, is often the cause FIG. 2t>. Ampeiopsis veitckn. 



Of the large yellow R > R < Stem-tendrils. (J nat. 



f /I 1 sizp -) 



areas frequently ob- 

 servable in the midst of clover fields. In 

 certain tropical parasites belonging to the 

 family Rafflesiaceae, the process of reduction 

 has advanced so far that the flowers alone 

 are left to represent the whole plant. Eafflesia 

 .l/'uoldi, a plant growing in Sumatra, is a re- 

 markable example of this ; its flowers, al- 

 though they are a metre wide, the largest 

 flowers in existence, spring directly from the 

 roots of another plant (species of Cisstis). 



Tendrillar Shoots. A peculiar form of 

 metamorphosis is exhibited by some climbing 

 of GietHt- plants through the transformation of certain 

 (4 nat. of their shoots into TENDRILS. Such tendrils 

 assist the parent plant in climbing, either by 

 twining about a support or otherwise holding fast to it. The twining 

 bifurcated tendrils of the Grape-vine, for example, are modified shoots. 

 In some sub-species of the wild vine (Ampelopsis Jtederacea) and in 



FIG. 30. Stem-tin. in 

 schia triawnthos. 

 size.) 



