98 UTRICULARIA [ch. 



when the plants are growing in a thick tangle that is to say 

 under circumstances in which the oxygen starvation, to which 

 submerged plants are liable, must be particularly acute. 



For the third type of modified shoot, the misleading term 

 * rhizoid' has been used; this name would have been more fitly 



Fig. 65. Utricularia vulgaris, L. Part of shoot with bladder-bearing leaves, and 

 an air-shoot (L). (Enlarged.) [Goebel, K. (i 891-1893).] 



applied to the 'earth-shoots,' since in function they approxi- 

 mate to roots, and to the 'rhizoid shoots' of Ceratophyllum'^. 

 The 'rhizoids' are developed at the base of the inflorescence 

 in certain species of Utricularia (R in Fig. 66). They bear no 



^ See pp. 88 and 89, 



