1 66 SCOTCH PINE. 



Although the guard cells of the stomata appear at 

 first sight to be deeper seated than the epidermis, 

 observation teaches that they have been pushed down 

 by the crowding over them of the adjacent epidermal 

 cells, and here, as always, belong to the epidermis. 

 This is confirmed by examining younger stomata. 



The partial partitions by which the mesophyll cells 

 are distinguished are explained by Sachs" as intru- 

 sive foldings due to local growth of the wall at the 

 point where the fold occurs. Corry 28 however asserts 

 that there is no real, but only apparent ingrowth, 

 which is caused in this way : when the cells are still 

 small their nuclei are attached to the protoplasm lining 

 the wall by delicate protoplasmic strands one or more 

 of which at a later period become converted into cel- 

 lulose thus attaching the nuclei firmly to the wall. 

 When the cell enlarges these points are firmly held 

 near the nucleus. Since some of the strands soon 

 break, many of the infoldings are shallow while others 

 holding, cause deep infolding. 27 The purpose of these 

 infoldings is considered by Haberlandt to be to 

 secure a greater surface on which to display the 

 chlorophyll bodies. Corry says of them : " They per- 

 form at all events a very obvious and noteworthy 

 function in forming the intercellular spaces beneath 

 the stomata in Pinus, and in producing air channels 



25 Text-book, 2nd Eng. ed., p. 74. 



26 On some points in the structure and development of the leaves of 

 Pinus sylvestris. Proc. Camb Phil. Soc., iv (1883), p. 344 et seq. 



27 Similar infoldings in leaves of Elymus Canadensis and other grasses 

 are described by Kareltschikoff (Bull. Imp. Soc. Nat. Moscow, xlt 

 [1868], p. 180) and in Caltha palustris, Anemone nemorosa and a 

 number of other plants by Haberlandt (Oester. Bot. Zeit, xxx [1880], 

 P- 305). 



