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Viiollier iind stronger pronf iIimI the liii ni ihc root is so valiialilr an absorp- 

 tive organ is tlic (.'Xtraordinary development of the i-ondnetive tissne of the root 

 to a proximity of the tij) wholly nnlike that found in other plants. This unusual 

 -develoiimcnt would indicate that the planJ obtained through the vascular tissue 

 from the tip a |)art of its food supply. Sucii a condition of unusual development 

 of vessels at unexpected places is to he noted in various plants, and indicates the 

 dependence on that jiart for supplies of moisture. This is true, for example, of 

 those ))arts of pitcher jilants that retain supplies of water, without whicli tlie 

 plant woulil wilt. (King and Zimmerman, lS8o.) On the other hand, acpiatic 

 ;in(l >emi-a(|iiatic jjlants often show poorly develoi)ed root-caps, or freqnenth' the 

 cap is attached only at the very tip, thus allowing the water free contact with the 

 epidermis, hut a few cells back from the initial group. 



The need of the root cap as an organ of protection in Poyoma ophioc/losiioidc.'i can 

 eei-tainly not overbalance the increased efhciency of that part of the root due to its 

 absen<e. The loose nature of the sphagnum does not offer any resistance to the 

 growing root, while it at the same time affords an efficient protection. It is true that 

 aerial and a(|uatic roots are not required to force tlieir way through tlie medium in 

 which they grow, but at the same time tlie air and water do not protect the a'oots as 

 does the moss, and, further, in the case of aerial orchids the outer cells' of tlie root 

 caj) do not drop away to any gifat extent, and the whole tip of the root may liecome 

 turgid and capable of absorbing moisture, thereliy aecomidishing the same end in 

 this respect as would be reached were the root cap not present. No doubt the in- 

 creased activity of the tip would make it more sensitive, and, as the recent in- 

 vestigations of Pfeffer (Annals of Bot., Sept.. 18!l4, ) show the irritability of the 

 root to be confined to that jjart. this would certainly be of great advantage to the 

 plant. 



It would seem, in view of what has been said, that the absence of this cap in 

 I'dijonin ophior/loxsoidea is not the effect of degeneration, but rather the attainment 

 <if a greater stage of perfection, tiue to the jirinei])ies of evolution, whereliy a 

 useless organ has degenerated and disappeai'cd. and in so doing worked material 

 ■advantage to the organism. 



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