The Determinative Action of Environic Factors Upon Neobeckia acquatica Greone. 27 1 



being irregularly bi-pinnate with ultimate segments more than I mm 

 wide. About the end of December grubs attacked two of the plants 

 and they lost all of their foliage. The roots were saved and a new 

 crop of leaves soon appeared which were very finely dissected with 

 segments less than 1 mm wide. Within a month after the* appearance 

 of the fine leaves on these plants the same sort of leaves were appearing 

 on the plants which were not attacked. The avers^e length of the 

 leaves was 6 to 7 cm. From February untU May the plants did well 

 but underwent no further changes of leaf form." 



Still another series of cultures in the soil were carried out in the 

 glass house attached to the Desert laboratory at Tucson, Arizona. Three 

 introductions have been made, and material has been drawn from them 

 to various other places. Some individuals brought to Tucson in 1908 

 are still alive despite the extreme summer temperatures to which they 

 are exposed {100» F to 1200 p). Establishment in the soil at this place 

 was invariably followed by the appearance of nepionic leaves merging 

 gradually into aerial dissected forms. It was notable also that very 

 slight disturbances would cause rejuvenescence and a return to the 

 broadly laminar leaves, and those which were formed in the period 

 immediately following the cooler weather of January and February were 

 characterized by a spread and area of surface tar surpassing anything 

 seen in the natural habitat of the plant, and also all other experimental 

 conditions. 



A final introduction in September 1912 consisted of a number 

 of stems of aquatics which had been packed in wet moss and shipped 

 from the New York Botanical Garden by Dr. E. M. Kupfer. Those 

 placed in small aquaria containing spring or well water showed a 

 development of finely divided leaves from the terminal buds, while 

 awakening lateral buds unfolded the usual series beginning with broadly 

 laminar nepionic leaves. Other plants set iu the soil formed nepionic 

 leaves while plants already in position coincidently formed similar organs, 

 which might be attributed to the falling temperatures of the autumnal 

 season. It was notable that terrestrials at this place were extremely 

 sensitive to any disturbance. Stirring the soil around the thickened 

 roots would cause the crown buds to unfold nepionic leaves. These 

 plants remained in the rosette stage and the apex of the stem did not 

 rise above the level of the ground at Tucson. 



About the 1^' of December 1912 it was noted that the divisions 



of the leaves on terrestrials and aquatics were very similar both in pattern 



and in the fact that the ultimate divisions were flattened and strap-shaped. 



18* 



