I INTRODUCTION 41 



We now come to the question of triangular stems. 

 Tliey occur principally among Monocotyledons. While 

 among Dicotyledons the number of 

 parts which go to make up a whorl 

 is generally four or five, in Mono- 

 cotyledons the number is frequently 

 three (Fig. 28). Moreover, the base 

 of the leaf usually encircles or 

 sheathes the stem or base of the next 

 leaf. No doubt, as we have already ^i<^- 28.— Arrangement of 



, T • • , 1 ■ . leaves of Carex. 



seen, there is m this arrangement 

 some loss of strength. This is not, however, of supreme 

 importance as the plants in question, being compara- 

 tively small, grow in sheltered situations and in close 

 association, so that each is protected by the rest. 



The triangular form prevails among the Rushes, 

 Bulrushes, Sedges, etc. It is not, however, universal 

 in Monocotyledons. Grasses, as we all know, have 

 round stems. In fact. Sedges may generally be known 

 from Grasses in this way. Sedges have triangular 

 stems, Grasses have round stems. While the leaves 

 of Sedges and the parts of the flower are in threes, 

 those of Grasses are often in twos and the leaves 

 are "distichous," i.e. in two rows or ranks (Figs. 

 28 and 20). It is remarkable, however, that one 

 Grass — a Chinese species of Bamboo — has a quad- 

 rangular stem. It is so remarkable that it long ago 

 attracted the attention of the Chinese, who attribute 

 the origin to the fact that one of their holy men had a 

 squared walking-stick made of this Bamboo. He stuck 

 it into the ground, and, in consequence of his sacred 

 character, it at once grew, retaining, out of respect to 

 him, its square form. 



The flinty stems of Grasses help to increase their 

 rigidity, and are probably also a protection against 

 snails and other animals. 



The stem of trees, as a rule, is thickest at the base, 

 where it requires to be firmly anchored in the ground, 

 then diminishes for a few feet, gradually reaching a 



