Stems and Petioles of Tropaeolum peregrinum , L. 591 
but this appearance is only due to the refractive character of the protoplasm 
at the tip of the hair. 
The hair cells are seen to occupy a position comparable to that of the 
stomata in relation to the ordinary epidermal cells of the stem when a surface 
view or longitudinal section of the stem is examined. The epidermal cells 
are elongated, while the cell from which a hair arises is almost circular in 
outline. No such small cells could be seen except when a hair was either 
in process of formation or had already been formed. It would seem, there- 
granular contents. 
Text-fig. i. A small piece of 
stem showing hairs. 
Text-fig. 3. A slight- 
ly later stage, the cell 
forming a papilla. 
fore, that the stimulus caused by the removal of the laminae induced division 
in some of the epidermal cells, and that one of the products of the division 
gives rise to a hair, while the other elongates to form an ordinary epidermal 
cell. Such cell-division appears to take place near the apex of the stem 
when the tissues are still quite young, but it is also clear that hair mother- 
cells may be cut off from epidermal cells in older portions, as it has been 
noticed that the longer the plant is deprived of its laminae the denser the 
hairs become throughout the whole portion of the stem which is still capable 
of growth. 
As far as I am aware very little has been done in the way of attempts 
