— 9 — 



especially noteworthy since Goebel ! states that the vegetative 

 reproduction of mosses has this peculiaritj^ that the formation 

 of new leafy shoots is always preceded by the production of 

 a protoneraa. 



From the above experiments it is demonstrated that 

 there is no inherent tendency to the production of rhizoids 

 or buds from a particular side of the leaf; that buds are 

 not produced in darkness, either because the photosyntactic 

 processes cannot be active or because light in itself is necessary. 

 The greater production of rhizoids from the free side of the 

 leaf in the dark would indicate that illumination exercised 

 a retarding influence upon their production. The growth of 

 the rhizoids from the contact surface of the leaf may be 

 due either to contact or gravity, or both. 



In order to determine the part which contact and gravity 

 play in the direction of rhizoid growth, the following 

 experiments were carried out. Leaves were placed on filter 

 paper and grown in the dark in an inverted position, and 

 in these cultures the same as in the ordinary position, the 

 leaves produced rhizoids mostly from the contact surface. 

 In order to render the supply of moisture of both surfaces 

 as nearly equal as possible, the leaves were grown in a 

 saturated atmosphere. Other leaves grown in both light 

 and dark between two sheets of filter paper showed a pro- 

 duction of rhizoids about equally from both surfaces. Again, 

 leaves which were grown in a vertical position produced 

 rhizoids radially in all directions. These experiments then 

 show that the rhizoids are not influenced as to their point 

 of origin by gravity but more by contact. Leaves were also 

 grown in soil with about the same result except that a 

 greater number of rhizoids originated from the surface of 

 the leaf nearest the air. The formation of buds upon the 

 leaf in the ordinary manner was naturally prevented and 

 when the rhizoids reached the surface of the soil and were 



1 Outlines of Classification, p. 170. 1887. 



