76 



ON THE PLANT-CELL. 





sarilj playing with words. From a long series of researches I have 

 come to the conclusion, that in at least two thirds of the whole vegetable 

 kingdom the function of the two semi-lunar cells of stomates is no 

 way different from the ordinary cells of the leaf. That in the other 

 cases these cells act as glands, I do not at all believe. 



Appendicular Organs. Although the epidermal cells are universally 

 the first in which the process of growth ceases, yet it often continues in 

 particular spots. The most simple form 

 is the mere extension of the external 

 cell-wall into longer or shorter papillae, 

 which give to petals their peculiar as- 

 pect, and roots their hairy appearance 

 (fig 87.). Frequently these papillary 

 growths exist only at particular spots, 

 and the papillaa develop from two to five cells, which at first are round, 

 but afterwards become extended, and thus form a cellular upright hair 

 of the epidermis (fig. 88.). This is the general way in which hairs are 





87 Papillary epidermis from the under surface of the petals of Iris variegata, with 

 underlying cells of parenchyma. 



88 c, Epidermis, with simple hairs, from the stem of an (Enothera. a, Club-shaped 

 hair, b, Pointed hair. 



89 Part of the epidermis of the leaf of Helleborus faetidus, with two hairs. Every hair (a) 

 is swollen and club-shaped above, and appears to contain a poisonous secretion. The hair 

 becomes gradually empty, and falls in, as seen at b. 



90 Stellate hair of Alyssnm rostratum. a, Its point of attachment. 



91 c, Epidermis, and d, the parenchyma, of Alte.rnantlie.ra axillaris, with a single hair. 

 This consists of a series of flat cells at the base (6), and a multiform thick-walled coll 

 above, a, Spot where a branch of the cell has been removed. 



