410 Rennert : The Phyllodes of Oxypolis filiformis 



none of the difficulties of absorption of the liquid in bogs. These 

 submerged individuals as well as those in the bell-jars were seen 

 to undergo true aquatic adaptations consisting in the loss of hypo- 

 derm of the central stellate tissue and of the glands ; the reduction 

 of the chlorophyl-bearing elements, of the endoderm, and of the 

 number of stomata as well as of the xylem ; the change in the 

 position of the resin duct ; the modification of the epidermal cells^ 

 stomata, cells of the septa and the course of the bundles through 

 the septa ; and the adoption of a new method of propagation. 



These changes may be divided naturally into two classes, those 

 which involve a suppression of xerophytic characters and those 

 which are a means of adaptation to moist conditions and therefore 

 hydrophytic in their nature. In the first class we must consider 

 the loss of hypoderm and glands, the reduction of palisade-cells 

 and water-storage tissue of the endoderm and the loss of cuticle ; 

 while we find in the modification of the epidermal cells, the re- 

 duction and modification of the stomata and the adoption of a new 

 method of propagation types of structure peculiarly distinctive of 

 hydrophytes. If the action of water free from high concentration 

 of osmotic substances will induce such sweeping departures from 

 the normal, it seems but reasonable to conclude that the plant is 

 naturally a swamp xerophyte. 



The adaptations described seem to have been most thoroughly 

 adopted by the species since the characteristic structure of the 

 phyllodes is to be found in the seedlings. These seedlings were 

 raised from seed developed by the plants with which the ex- 

 periments were made. The cotyledons were flat and linear in 

 shape and 5 to 6 cm. in length. When the first leaf developed it 

 exhibited the typical awl-shaped, septate character and bore glands 

 and the accompanying scales along one side throughout its length. 

 In internal structure it also resembled the later leaves in all re- 

 spects, except that the hypoderm was absent and that the cells of 

 the endoderm bore chlorophyl. 



The chief results of importance brought out in the foregoing 

 paper may be briefly summarized as follows : 



I. The leaf-structures of Oxypolis filifonnis are terete, awl- 

 pointed phyllodes with numerous septa or diaphragms, and this- 

 form is exhibited even by the first leaf of the seedling. The 



