CHAPTER XXXVI. 



THE RELATION OF SIZE AND FORM IN PLANTS. 



The Obconical Form. 



Living Plants have now been considered in their various aspects of 

 Form, Structure, Function, and Propagation. But there is still 

 another point of view which emerges as the result of comparative 

 measurement. A relation has thus been found to exist between Form 

 and actual Size ; but hitherto its 

 study has been almost wholly omitted 

 from the general discussion of the 

 plant-body. Moreover, there has 

 been a very frequent neglect of uni- 

 formity in scale of the illustrations 

 used in comparison, which has tended 

 to obscure the issue. But once the 

 relation between Size and Form is 

 brought into view on a uniform scale 

 of measurement for each example, 

 many observed data acquire new 

 meanings, both functional and evol- 

 utionary. 



The discussion of this relation 

 starts from the fact that green 

 plants are accumulators of material 

 gained by photosynthesis. They are 

 in no equivalent degree expenders. 

 Hence they naturally work to a 

 favourable balance of material. As the surplus of supply is u 

 up in the growth of a plant of primary development, which has 

 polarity in relation to some fixed -tame, its outline tends to expand 

 from the base upwards, and the plant takes a more or less obconical 

 form, with the vertex or cusp directed downwards. A simple example 

 of this type is seen in the young plant of Fucus (Fig. 445)- I* : 



589 



Fin. 4 

 Young spon .-linn "f 1 ' ncus MttCttJOMH in 



longitudinal and • 



Rostafinsld.) The form is obconical, with 

 circular transverse outline : it is only lata 

 that it 1 ■• laterally oompreawd up- 



ward-. (Sei 



