The Genus Phyllospadix 407 



the branch, affording at once an even support in the sand or 

 on the rock, and balance in the water, very complete and ef- 

 fective as a mechanical arrangement calculated to resist great 

 strain. 



Zostera, accustomed for the most part to protected waters and 

 more or less muddy bottom, has numerous weak roots in ir- 

 regularly placed cushions, and the more fragile leaves exhibit 

 no especially effective means of bud-protection. 



The fibro-vascular bundle-traces (C) show that the leaf- 

 trace, and the root-trace in the " internode " behind it arise 

 from nearly the same plane and simultaneously, the leaf and 

 roots themselves never being far separated when fmature. 

 The bundle-trace to the branch has a very different origin, 

 and at no time appears axillary. In the older parts of the 

 rhizoma there are three fibro-vascular traces (the vascular 

 system weakly developed), but the lateral ones are not in a 

 plane with the branches and roots. At each branching of the 

 central trace, however, toward the leaf or roots the lateral 

 traces send in to its support tributary horizontal branches. 



The leaves, mostly from sterile branches, are numerous, 

 slender, smooth, coriaceous, dark-green, from one to two and 

 one-half millimeters in width, oval in cross-section, and 

 usually from one to two and one-half meters long. They are 

 provided with sheaths from ten to thirty centimeters or more 

 in length, opening at the side and ending in short, rounded 

 stipules. The numerous small nerves of the sheath are re- 

 solved above into three, which continue through the length of 

 the long lamina to near its two-lobed extremity. At intervals 

 there are simple cross-veinlets. The extremities of the 

 young and still enclosed leaves are beautiful objects, from 

 the development of the ruffs of "fin-cells," transparent, of 

 various forms, and arising from the leaf a little within the 

 margins (Fig. K). These persist after the leaf is free in the 

 water. Similar structures are known in species of a few re- 

 lated genera. 



The slender (one to two millimeters in width) flowering 

 stems, are from lateral branches, and are concealed and pro- 

 tected by the more distal leaves of the leaders. They are 



