304 



Holm — Studies in the CyperacecB. 



hadrome of nearly all the mestoine-bundles. The rhizome 

 shows thus a dense and solid structure with no trace of lacunes 

 or even ducts, the cells of the bark-parenchyma leaving only 

 very narrow intercellular-spaces. 



The root shows a very sim- 

 ple structure, which agrees in 

 all respects with that of the 

 Cyperacece in general. The 

 epidermis becomes thrown off 

 by age, but is then substituted 

 by a thick-walled hypoderm, 

 which surrounds the very open 

 bark - parenchyma, showing 

 numerous lacunes, which have 

 arisen by the tangential col- 

 lapsing of the bark-cells. The 

 innermost bark is differentiated 

 as a very thick-walled and por- 

 ous endodermis {End in figure 

 4) which surrounds the peri- 

 cambium; this last is as usual 

 the Cyperacece (with the 



Fig. 4. Transverse section of a root 

 B, the bark-parenchyma . End, Endo- 

 dermis: P. Pericambium; PL, Proto- 

 leptome ; PR, Protohadrome. 400 x 

 natural size. 



Ill 



only exception of Car ex Fra- 

 seri, so far as is known) inter- 

 rupted by elements of protohadrome, which therefore lie close 

 up towards the endodermis. In alternation with the proto- 

 hadrome are to be observed small groups of protoleptome, 

 while the center of the root is occupied by a huge vessel, sur- 

 rounded by a few layers of conjunctive tissue. 



This is the general structure of Dichromena leucocejphala, 

 and if we now institute a comparison of these structures with 

 the corresponding organs of D. latifolia, we may be some- 

 what surprised to find exact uniformity rather than any dif- 

 ferences. Both plants have long been unanimously recognized 

 as distinct species, although the differentiation seems to have 

 been based on so slight a character as " the tubercle of the 

 achene being decurrent down the margins." This character 

 did not, however, seem sufficient to Kunth for separating them 

 as two species, and he therefore did not accept the species 

 latifolia without a certain reservation and doubt : " Dichro- 

 mencB leucocephalce affinis, sed major. Mihi adhuc dubia." 



A comparison of their structural characters may simply be 

 expressed in this way, that the mechanical tissue is somewhat 

 more strongly developed in D. latifolia^ but otherwise no dif- 

 ference was to be detected. That this uniformity in anatomical 

 structure, as observed in the most important organs of the 



