Osborn. — Some Observations on the Tuber of Phylloglossutn . 505 
dilates at the distal end to form a chamber into which the growing-point 
projects (Text-figs. 41 and 42 and Photos 7, 8, 9, and 11). 
In the majority of cases it is not until the apex is well buried that 
growth takes place in all directions, resulting in a tuber. This has the usual 
conical meristem seated on a spherical mass of parenchyma (Photo 7). All 
the essential features of a normal tuber of Phylloglossu m are shown in this 
section made from a detached leaf after three months’ growth. At this 
Text-fig. 40. Transverse section of leaf ; epidermis indicated by faint line. An irregular cell 
mass has formed, and the growing-point has begun to invaginate. c. — opening of channel, v.b. 
— vascular supply of leaf. Camera lucida outline. x 26. 
Text-fig. 41. Portion of longitudinal section through cell mass, stalk (which was accidentally 
bent), and tuber. ‘ Vascular supply ’ seen from its expansion in cell mass to cup of * tracheides’ 
around growing apex ( x ). Apex projecting into the chamber and seated on spherical mass of 
starchy tissue. The whole length of channel shown, c = opening of channel. Camera lucida 
outline, x 26. 
Text-fig. 42. Longitudinal section of adventitious growth on leaf in Fig. 20 B. Apex ( x ) seen 
projecting into chamber ; extent of starchy tissue shown by faint line. Greater part of ‘ vascular 
supply * seen, extending towards * leaflet ’ (/.) (which passes out of plane of section), but no 1 leaflet ’ 
bundle differentiated. Camera lucida outline, x 26. 
stage, however, tuber and dropper consist entirely of parenchyma. Sub- 
sequently a 4 vascular supply ’ is developed and differentiation proceeds 
within the tuber. 
The ‘ vascular supply ’ consists of a strand of tracheidal cells, with 
loose spiral or reticulate markings, extending from the original cell mass 
along the dropper to a point at the level of the apical meristem. This 
development is most active during the last month of growth, and results in 
the lignification of certain of the parenchyma cells. These agree with their 
