STRUCTURE, MORPHOLOGY, AND PHYSIOLOGY. 5 



development of the internodes. Such tufts are also found 

 upon the upper nodes and runners of some grasses, for 

 example Sporobolus, Cynodon, JEluropus, and CMoris, 

 whenever a well-developed internode is followed by 2-4, 



Fig. 2.— Cross-section of a fibro-vascular bundle from the culm of Maize (X 550). 

 p p. Surrounding parenchyma (a, outer side; i, inner side), g g, Pitted vessels: /, 

 air-passage with isolated ring, ?-, from a former ring-vessel; v v, sieve-tubes. 

 The shaded cells in the circumference are those of the sclerenchyma threads ; 

 those between g and g are very narrow pitted vessels; s, a spiral vessel. (After 

 Sachs.) 



shortened, nodeless ones. Every branch begins with a 

 two-keeled, rarely {Cynodon) two-cleft, membranous 

 prophyllum with its back towards the main axis, and is 

 followed by the other leaves in such a manner that their 

 median plane crosses with that of the prophyllum and 

 the leaf in whose axil the branch originates. The sue- 



