HISTOLOGY OF riTCHER- PLANTS. 153 



the outgrowth and subsequent division of a single surface cell ; that 

 surface glands maj consist of a single surface cell, unaltered in 

 form, but assuming a different function, or divisions may arise in 

 one or more of these cells prior to or at the same time that the new 

 function is assumed ; while sub-epidermal glands are the result of 

 the modification of cells which originally occupy that position. 



Another curious thing is that Dr. Tait should refer to Drosera 

 and Pingtiicida for examples of included glands. In the former we 

 have only two forms of glands, viz., the large ones at the summit of 

 the tentacles and the small sessile ones which are found both on the 

 upper side of the lamina of the leaf and on the tentacles as well. 

 The latter, wherever they exist, are certainly surface glands, the 

 upper cells being slightly elevated above the general level of the 

 surface upon which they are found. 



But the reference to Pinguicula is the most extraordinary ; and 

 how our author could have arrived at the conclusion that the 

 glands of this ])lant '' occupy the spaces between the large cells 

 of the parenchyma," passes my comprehension, as they are 

 most undoubtedly glandular hairs, having a distinct unicellular 

 pedicel. 



Farther on we have another paragraph, which appears to me as 

 very remarkable. It runs as follows "Another variety of epi- 

 thelial absorbent is the tubular trichome found in certain pitchers. 

 It is always associated with a system of intercellular canals, and 

 seems really to be developed from the protoplasm contained in these 

 canals more than from a cell, the cell wall apparently going to con- 

 stitute the lining membrane of the tube, its protoplasm disappear- 

 ing. At the upper side of the margin of the base of the trichome 

 its protoplasm can be seen to be continuous with that of the inter- 

 cellular canals ; and in the growth of the hairs this can be seen to 

 be deepening in colour and increasing in quantity at the lower part, 

 so as to form the process of the trichome." 



In the next paragraph he also says : — " The system of inter- 

 cellular canals to which I have referred are best seen on such sur- 

 faces as absorb digested food. Thus on the inner surface of a 

 Nepenthes pitcher examination by high powers will demonstrate 

 these canals beyond dispute. They are walled and contain proto- 

 plasm, for its columns may be seen broken at irregular spots." And 

 again : — " The most complete proof of the actual existence of these 

 canals is to be obtained from diseased epithelial surfaces where 



