GENERAL MOEPHOLOGY OP THE PLANT 45 



of a leaf at its base, which continues the growth in length, caus- 

 ing the formation of a sympodium, as in Solomon's Seal ( fig. 

 59). 



f. The Phylloclade. — In some plants the leaves are very 

 feebly developed and soon fall off, or are modified into spinous 

 or needle-like processes. In such oases the stem performs the 

 functions of the leaves, becoming green and assuming a 

 flattened or rounded form. Such a siera is caReA a, phylloclade. 

 Examples may be seen in many Cactuses, where the stem is 

 either globular, or composed of flattened or round joints, or of 

 winged columns. In certain Liliaceae the phylloclade has the 

 shape of an ordinary foliage leaf, from which it can be dis- 



FiG. 67. 



Fig. 67. Creeping stem of the Sand Carex (Carex arenaria). 1. Terminal 

 bud by whicli tlie stem continues to elongate. 2, 3, 4. Shoots produced 

 from former buds. 



tinguished by bearing leaves and flowers, either on its margins 

 or at some point on its surface. Such a branch consists only 

 of one internode ; it is soft and pointless in Myrsiphylluni ; firm, 

 hard, and spiny at its apex in Bxlscus aculeatus. Its stem- 

 character can be seen also from its arising from the axil of the 

 true leaf, which is very small and soon falls off. Phylloclades 

 of this kind have also been called cladodes. 



g. The Thorn. — It sometimes happens that a leaf-bud, 

 instead of developing as usual, so as to form a symmetrical leaf- 

 bearing branch, becomes arrested in its growth, and forms a 

 hardened simple or branched projection terminating in a more 

 or less acute point, and usually without leaves, as in Crataegus 

 Crus-galU {fig. 63), Qleditschia {fig. 62), and many other plants. 

 Such an irregularly developed branch is called a thorn. That the 



