270 ^^'^ Dougal, 



divisions were irregularly oval in cross section, and had an epidermis 

 of flattened elements against which the underlying parenchymatous 

 tissue three or four layers in thickness was crowded. These thin-walled 

 cells were irregularly cylindrical and arranged without intercellular 

 spacing, with their longest axes parallel to that of the filament of which 

 they formed a part (Fig. 9). Whatever the relation may be it was 

 noted that whenever regenerating cuttings floating in the water were 

 anchored, the influence of the anchorage was to cause the nest leaves 

 formed to take on some of the characters of terrestrials ahhough these 

 organs were some distance below the surface. Thus in 1913 cuttings 

 which had progressed so far as to be forming aquatic leaves with 

 thread-like segments, began to make strap- shaped divisions when the 

 plantlets were fastened in the soil at the bottom of the dish. 



Some of the experiences with this plant in various climates show 

 the manner in which developmental proceedure might take place in 

 dissimilar complexes of external conditions. 



Six clumps ol plants grown as terrestrials at the New York 

 Botanical Garden since 1902 were received at the Desert Laboratory 

 March 17, 1906, and were kept in pots until they were taken to the 

 Montane plantation just being established in the Santa Catalina moun- 

 tains at 8,000 ft. in May. The history of these plants shows that they 

 underwent changes by which broadly laminai- nepionic leaves would be 

 produced from the buds to be followed by others of the finely dissected 

 types. These alternations were not seasonally regular however. In some 

 instances nepionic leaves were formed jn midsummer with the advent 

 of the rainy season to be followed by a series running to aerial 

 dissected types. 



Some material was taken to the Cinchona station of the New York 

 Botanical Garden in the Blue mountains of Jamaica (7,345 ft.) by Dr. 

 Forrest Shreve and the notes communicated by him read as follows: 



„Tlie four plants of Rorjpa americana taken to Cinchona were 

 set out in the pots about October 23^ 1905 at different points in 

 the beds or borders such as gave them different amounts of light or 

 shade. The pots were merely sunk in the ground until the tops were 

 flush with the level of the beds and the water received by them was 

 only the natural precipitation. During November a number of leaves 

 appeared which were entire and bluntly dentate, being rather spatulate 

 in outline. These were quickly followed by leaves which were similar 

 in the upper part to those just described but were lyrate at the basal 

 portion. These were in turn followed by leaves which were rather fmely cut, 



