50 



PRINCIPLES OF PLANT-TERATOLOGY. 



with the protonema into which it may change under 

 certain circumstances. 



This transformation of the rhizoid into a protonema 

 may therefore be mentioned as one of the main abnor- 

 malities which it exhibits. Conversely, the protonema 

 may change into a rhizoid. Kiitzing placed detached 

 leaves of the moss Bryum pseudotriquetrum on sand, 

 when the cells grew out into protonemal filaments 

 which became rhizoids at their ends. Schimper also 

 saw protonema-buds arising from the lower surface 



Fig. 11. — Funaria hygrometrica. Protonema threads springing from 

 basal end of leaf. (After Schimper, in part.; 



of the leaves of the mosses Orthotrichum Lyellii and 

 0. obtusifolium, which grew into rhizoids (PI. IV, 

 fig. 5). 



Kny describes, in Marchantia polymorjpha and Lunu- 

 lariu vulgaris, a curious kind of pseudo-proliferation 

 of the rhizoid. Secondary and tertiary rhizoids were 

 observed to arise successively within the primary one, 

 giving the appearance of three tubes, one within the 

 other (PI. IV, fig. 9). In other cases there occurred 

 two or three side by side within the primary one. 

 These supernumerary rhizoids arose from the layer 

 next within that from which the normal ones arise. 



