Osborn. — Some Observations on the Tuber of Phyllog lossum. 503 
from those abnormal cases in which a number of minute tuberous bodies is 
formed (e. g. Series A) that each may arise from the activity of a single 
epidermal cell (Text-fig. 36). 
The epidermal cells, which are considerably elongated in the direction 
Text-fig. 36. Portion of transverse section of leaf showing adventitious growth from single 
epidermal cell. Stomate seen to left, x 180. 
Text-fig. 37. Transverse section of leaf showing considerable cell mass of epidermal origin, 
interrupted by stomate at St. Growth is becoming localized by development of growing-point 
seen at right, x 44. 
Text-fig. 38. Transverse section of leaf (see Fig. 23). Two growing-points are developing; 
the anticlinal walls separating the groups of epidermal cells involved are plainly seen, x 44. 
Text-fig. 39. Portion of longitudinal section showing junction of leaf tissue and cell mass 
showing epidermal origin of latter. Cell mass developed stalk in which a ‘ tracheide ' is seen. 
X44. 
of the leaf axis, first divide transversely, and at the same time the seg- 
mented cells enlarge in a radial direction. The radial elongation is accom- 
panied by periclinal division. 
O O 2 , 
