30-1 T. Holm — Studies in the Cyperacece. 



with long sheaths in contrast to the umbellate inflorescence in 

 Cyperus with sheathless, involucral leaves. Otherwise we 

 iind in Dulicliium, as already described, the same fore-leaves 

 though weakly developed, since they are hidden in the sheaths 

 of the bracts, and have not the same function as those in 

 Cyperus. The terminal inflorescence in Dulichium corresponds 

 to that of Cyperus, but is raised high above the lateral ones, on 

 account of these being scattered along the stem and borne on 

 relatively short peduncles. 



In speaking of the function of the clado-prophyllon in 

 Cyperus, we might state at once, that it is by means of this organ 

 that the rays of the umbel attain their more or less horizontal 

 position. This is readily perceivable when we compare a young 

 inflorescence with an older one. Because it is a well-known 

 fact that before the stamens and pistils are fully developed, 

 the rays and the spikes are all erect and congested. But a little 

 before the flowers are ready for fecundation the rays spread 

 out, forcing the involucral, sheathless leaves to attain the same 

 position, and the spikes themselves gradually bend downwards 

 (Mariscus) or horizontally (Cyperus proper, Pycreus and Dicli- 

 dium) by the swelling of the small, basal prophylla (P 2 and P 3 ). 

 This movement is best noticeable in the large, tubular prophylla 

 (P 1 ) at the base of the rays, and we might, thus, briefly describe 

 the structure of these organs in order to show, how the move- 

 ment takes place. The fore-leaves (fig. 2) are tubular with a 

 short, free apex, and they show, when mature, a very prominent 

 swelling at their base and on that face which morphologically 

 is the dorsal ; the swelling, sometimes, attains the dimensions 

 and shape like a spur, while the rhachis itself remains slender 

 in its entire length. It is, thus, on the dorsal face of the pro- 

 phyllon that a parenchymatic tissue rapidly develops, a tissue 

 which in most respects agrees with true collenchyma ; it is com- 

 posed of short, somewhat thick-walled cells without chlorophyll 

 and no mestome-bundles are located in this tissue. The rapid 

 growth of this particular and very local tissue naturally pro- 

 duces a swelling of the leaf-base, and the result is, that the 

 respective ray becomes pushed away from the central and ter- 

 minal rhachis of the main inflorescence. (R 1 in fig. 1.) Other- 

 wise the structure of the prophyllon shows no deviations from 

 that of an ordinary leaf -sheath. 



Although the base of the ray, which is surrounded by the 

 prophyllon, remains slender, it nevertheless possesses some 

 layers of similar, collenchymatic tissue, the presence of 

 which greatly facilitates the movement from the vertical to 

 the horizontal position, forced by the increased growth of the 

 prophyllon. The small fore-leaves at the base of the spikes 

 * This Journal, vol. iii, p. 429, 1897. 



