No. 626] SHORTER ARTICLES AND DISCUSSION 



275 



with uninjured roots, grown as water-^cultures in distilled water, 

 also produced the juvenile leaf form, while those grown in a com- 

 plete culture solution developed their laminae normally. 



The same observer recorded a ease in which a plant of Hydro- 

 cleis nymphoides Buchenau (Butomacea3), which had heen bear- 

 ing the mature form of leaf, was observed to revert to the ribbon 

 form. On examination it was found that most of the roots had 

 died off. When a fresh crop of roots was produced, the mature 

 type of leaf occurred again. 



Another writer, Montesantos, showed by a series of experi- 

 ments upon Limnohium Boscii (Hydrocharitacese) that, in this 

 case also, the heterophylly is not a direct adaptation to land or 

 water life, but that the floating leaves are " Hemmungsbil- 

 dungen" due to poor nutrition. In the water soldier, Stratiotes 

 aloides, also, he showed that the stomateless leaves were primarj^ 

 but that their production could be induced at later stages by un- 

 favorable conditions. 



An experiment tried by Goebel on Sagittaria sagittifolia indi- 

 cated that absence of light in this case inhibits the formation of 

 leaves of tlie aerial tyi)e. An observation of Gliick's on Alisma 

 gramini folium Ehrh., also points to the same co'iiclusion. But it 

 seems probable that the effect produced in these cases was not 

 due directly to the darkness, but to tlio state of inadequate nu- 

 trition brought about by the lack of light for carbon assimilation. 



Among the potamogetons, again, experimental work by Esen- 

 beek has shown that reversion to juvenile leaves can be obtained 

 under conditions of poor nutrition. For example, when a land 

 plant of P. flmtans, which had been transferred to deep distilled 

 water, liad its adventitious roots repeatedly amputated, regres- 

 sion was obtained to the floating type of leaf and then the sub- 

 merged type. A similar reversion to thin narrow leaves was 

 brought about in the case of F. natans by growing the upper 

 internodes of a siioot as a cutting. 



Water lily leaves respond to experimental treatment in just the 

 same way as the mono(;otyledons already mentioned. In the 

 case of two species of Castalia, it has been found possible to in- 

 duce the mature plants to fonn submerged leaves, either by re- 

 moving the floating leaves or by eutting off the roots. This con- 

 firms an earlier suggestio^i, made by an rtaliaii writtM-. An-angeli, 

 that the development of the submerged le;iv,'s ,,t A ifiniJnia lutea 

 was due to "un indebolimento o diminu/iuiu' di ciKTLMa vitale." 

 This suggestion has roccivtMl iiidopendeiit, experimental confir- 



