The Determinative Action of Environic Factors Upon Neobeckia acquatica Greene. 273 





florescence- The conducting tract was strongly developed, but the 

 supporting tissue was weak. One or two layers of palissaded cells 

 were found underneath the upper surfaces and the remainder of the 

 chlorophyllose tissue was disposed in the form of spongy parenchyma 

 with large intercellular spaces. The epidermal cells over the midribs 

 and its branches were noticeably larger and had heavier walls than 

 elsewhere. These aerial dissected leaves by reason of the arrangement 

 of the dissues described are much more efficient transpiratory organs 

 than the terminal bract-like 

 leaves of emersed stems as 

 was evident seen by a com- 

 parison of the structure of 

 the two (Fig. 11). 



On May 19, 1904 the 

 cultures made from the cut- 

 tings o! 1902 were turned 

 out of the pots for exami- 

 nation. The large number of 

 lateral branches previously 

 mentioned had acted as off- 

 sets, from which new plants 

 had arisen, but still connec- 

 ted with the parent in such 

 manner that dense clumps 

 were formed. A compara- 

 tive examination of these 

 plants and others of the same 

 age and derivation grown in 

 the aquarium was made in 

 the latter part of October. 

 The normal aquatic spe- 

 cimens in July showed a 

 single main root not more 

 than 2 mm in diameter and 

 10 cm in length with a very 



thin secondary branches. The crown consisting of the top of the root 

 and a stem fused with it had sent off one or two branches- The 

 terrestrially grown individuals of the same age consisted of a clump of 

 thickened roots produced by numerous offsets and branches from the 

 crowns. These thickened roots were in clumps and were 10 to 15 cm 



j& 



J 



Fig- 12. Thickened roots of Neobcckia grown 



as a terrestrial. 



