148 



THE STEM PROPER 



lateral ones (Sec. 245). 1 The usurping bud continues the 

 growth of the shoot until it is in turn displaced by some 

 succeeding lateral one, and so on, forming a succession of 

 apparently lateral tendrils. 



212. Stems as Foliage. When branches take the place 

 of foliage, as they not infrequently do, they are generally 

 so much disguised that it is diffi- 

 cult to recognize them, but a 

 little attention to their point of 

 origin will usually make their 

 nature clear. The asparagus has 

 already been referred to (Sec. 68). 

 Still more striking examples are 

 found in the butcher's broom of 

 Europe (Riiscus aculeatus) and 

 the pretty little Myrsiphyllum 

 of the greenhouses, wrongly 

 called smilax, that is so much 

 used for decoration. The green 

 blades of these plants, which are 

 commonly regarded as foliage, are not true leaves, but 

 curiously shortened and flattened branches that have taken 

 upon themselves the office of leaves. Their real nature 

 is shown by the fact that they spring each from the axil 

 of a little scale or bract that represents the true leaf. 



PRACTICAL QUESTIONS 



1. Which of the stems named below are woody, and which herba- 

 ceous, or suffrutescent ? Blackberry, hollyhock, pokeweed, cotton, okra, 

 morning-glory, asparagus, garden sage, reed, corn, wheat, periwinkle, 

 sunflower, strawberry, bear's grass, broom straw. 



2. Why is it that so many, both of hot-weather and cold-weather 

 herbs, for example, knot weed (Polygonum aviculare), purslane, spurge, 

 carpet weed (Mollugo), winter chick weed, Indian strawberry, and dan- 

 delion, all adopt the same habit of clinging close to the earth ? (205.) 



3. Would such a habit be of any advantage to roadside weeds 

 and other herbs growing in exposed places where they are liable to be 

 trodden upon and bitten by cattle ? 



1 See also Gray's " Structural Botany," page 54, no. 



293. Stem leaves (cladophylls) 

 of a ruscus, bearing flowers. 



