Phytogeny of the Cyperaceae . 
27 
Summary and Conclusions. 
In the course of the present investigation a somewhat careful study 
has been made of the structural characters of some eighty species of 
Cyperaceae, representing seventeen North American genera. In addition 
to these, representatives of several other Monocotyledonous groups have 
been examined by way of confirmation and comparison. The following 
conclusions, based upon the results of this study, may be offered in answer 
to the questions propounded in the introductory paragraphs : — 
1. Amphivasal fibro-vascular bundles are continuous throughout all 
Cyperaceous rhizomes which bear conspicuous leaves at all of the nodes, 
and in which the internodes are relatively short (Amphivasae). Such 
bundles are absent from the rhizome only where the leaves are very small 
and widely scattered (Centrivasae). 
2. In the culms of the Cyperaceae amphivasal fibro-vascular bundles 
commonly occur only in the nodal complexes ; rarely such bundles are 
continuous through the very short internodes of the involucroid region 
of certain species. Elsewhere the bundles of the culm are strictly col- 
lateral. 
3. Amphivasal bundles are derived from collateral bundles by the 
multiplication of xylem-elements, resulting from the introduction of large 
and numerous leaf-traces into the central cylinder. In the Cyperaceae the 
amphivasal condition is not in any way related to the phenomenon of 
branching. 
4. A study of the Cyperaceae shows that the leaf is the dominant 
factor in the development of the stelar characteristics of the Mono- 
cotyledons. Branching of the axis does not affect the nature of the 
fibro-vascular bundles. 
5. The foliar fibro-vascular bundles pass downward through the culm 
as cortical bundles to the next lower node, where they fuse with the 
cauline bundles and with the subtending leaf-trace, through a ring-like 
amphivasal plexus. The cauline bundles pass continuously, but with nodal 
anastomoses, from the base of the culm to their termination in axillary 
buds or floral axes, or, less frequently, in nodal complexes. In the rhizome 
the course of the bundles more nearly resembles that which is typical of the 
Palm-stem. Fusions and anastomoses of the bundles of the rhizome take 
place chiefly in the superficial reticulum of the central cylinder. 
6. The simple tubular central cylinder which has been found in the 
seedling and the floral axis proper of all the Cyperaceae which have been 
examined is to be considered ancestral or palingenetic ; while medullary 
strands and the amphivasal bundles characteristic of most rhizomes and 
of the nodal complexes of aerial stems apparently must be regarded as 
more recently acquired or caenogenetic features. 
