viii] ' EARTH-SHOOTS ' AND ' AIR-SHOOTS ' 97 



In Utricularia minor ^ Bremii^ intermedia'^ and ochroleuca^ cer- 

 tain shoots are formed which bear bladders on leaves of a 

 reduced type {E in Fig. 63, and h in Fig. 64). These branches, 

 which are known as 'earth-shoots,' penetrate the mud at the 

 bottom of the water and apparently serve for purposes of an- 

 chorage, and for the absorption of raw food materials. They 

 have retained their power of entrapping small animals, but have 

 substituted the functions characteristic of roots for the assimi- 

 latory activities of the water-shoots. The bladders make 

 such efficient hold-fasts that, unless the soil be very soft, 

 it is difficult to pull the earth-shoots out of the substratum 

 without snapping the leaves and leaving the bladders behind. 

 Every transition can be observed between earth- and water- 

 shoots. 



The British species of Utricularia which produce 'earth- 

 shoots' never show the second form of modification, the 'air- 

 shoot' (L in Fig. 65, p. 98), which occurs only in L7. vulgaris and 

 in the closely allied IJ. neglecta. These curious organs were ob- 

 served by Pringsheim^, who did not, however, understand their 

 nature, but called them 'Ranken' (tendrils). It is to GoebeP 

 that we owe a very plausible suggestion as to their biological 

 value, and to Gliick^ a definite view as to their morphological 

 status. They are, apparently, reduced inflorescences, and their 

 function is said to be to serve as breathing organs and to connect 

 the submerged vegetative body of the plant with the atmo- 

 spheric air. In the case of Utricularia vulgaris^ the air-shoots are 

 fine, whitish, thread-like bodies, some centimetres long. They 

 bear very small undivided leaves, closely appressed to the shoot 

 and with stomates on their outer surfaces. The lower internodes 

 are much elongated. The tips reach the water surface and pro- 

 trude from it into the air, where the stomates can perform their 

 usual function. The 'air-shoots' are said to occur especially 



1 Benjamin, L. (1848) described U. intermedia as 'rooted,' so it is 

 evident that he had observed the ' earth-shoots,' though mistaking their 

 morphological nature. 2 PHngsheim, N. (1869). 



3 Goebel, K. (1891-1893). ^ Gluck, H. (1906). 



A W. P. 



