THE BLADE. 11 



dlrhotomiun und oiliers, liiivo well developed sheaths, but the 

 blades are midimeutavy. 



The blades of some leaves, like those of Leersia (rice cut grass) 

 and Zizania (wild rice), are not quite S3'nimetrical, or in other 

 words, the midrib is not quite in the middle of the blade. 



The blades of many grasses after getting something of a start, 

 may continue to elongate or they may cease to grow. In case 

 of Poa pratoisix (June grass), Dactylis glomerata (orchard 

 grass), and many more, there seems to be scarcely any limit to 

 the length they may attain. In a damp season, when the leaves 

 were sheltered by a^ hedge, tlie writer selected a leaf of June 

 grass, still green and vigorous to the end, in which the blade was 

 five feet and four inches long. , The place of growth for such 

 leaves is a rather light green semi-circle near the ligule. The 

 tip of such a leaf-blade is the oldest portion. The lower portion 

 may continue to grow as the end is crojaped by cattle. 



The blade always lias iq^per and lower surfaces unlike each 

 other. Some leaves are convolute (rolled into a cylinder), while 

 some are cpjiduplicate (or folded), like the two halves of a book, 

 shutting against each other. 



When very dry, eonduplicate leaves may become convolute, and 

 between eonduplicate and convolute vernation, we have all pos- 

 sible gradations passing insensibly into each other. Some leaves, 

 as those of Lolium rigidum, are eonduplicate towards the apex, 

 and convolute towards the base. 



Leaves of many exogenous plants, like most of our trees and 

 shrubs, drop by separating from the stem at a natural joint, but 

 the leaves of most grasses may die, become brown and dry, and 

 still remain attached to the culm. The leaves of a few grasses, 

 as the bamboos and Sparflna (cord grass), have lilades with an 

 articulation or joint at the base; and some leaves have petioles, 

 as Phariis, Pariava, and Leptaspis. 



