174 BOTANICAL GAZETTE [SEPTEMBER 
a protuberance which becomes divided very soon by an oblique 
wall, and the insertion of the successive walls then follows in 
rapid order. Buds may occasionally originate as side branches 
of the rhizoids from either surface, although this is rare in the 
normal development. At the end of six weeks the specimens in 
the dark showed no sign of buds, and the long unbranched 
rhizoids had attained a length of about one centimeter. The 
peculiar method of regeneration shown in these experiments is 
especially noteworthy, since Goebel * states that the vegetative 
reproduction of mosses has this peculiarity, that the formation 
of a new leafy shoot is always preceded by the production of a 
protonema. 
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; also 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 of 
gravity, or both. 
In order to determine the part which contact and gravity 
play in the direction of rhizoid growth, the following experi- 
ments 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 
production 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, 
Outlines of Classification 170. 1887. 
