104 



BOTANY. 



(h) Water-pores. De Bary* describee under this name some curious 

 stoma-like structures which occur on many plants. These, instead of 

 containing air in their cavities, normally contain water. Their guard- 

 cells, which are, in some cases at least, much like those of ordinary 

 stomata, are immovable, and as a consequence the pore is incapable of 

 enlargement or contraction. They are always found over the ends of 

 small bundles of spiral vessels, which appear to pass into the pore cav- 

 ities. 



One form of these may be readily examined in the leaves of the f uch- 



FIG. 93. 



FIG. 94. 



Fig. 93. Surface view of the water-pore on the extremity of the leaf -tooth of Fuch- 

 sia globosa. X 500. After Arthur. 



Fig. 94. Transverse section of leaf-tooth of Fuchsia globosa; cp, chlorophyll- 

 bearing parenchyma, within which is the fibre-vascular bundle ; ra, raphis-cells. X 

 125. After Arthur. 



sia, and the primrose (Primula sinensis). In the fuchsia they are found 

 in the papillae or small teeth on the margins of the leaves, and in the 

 primrose, in the papillae terminating the lobes and lobules. In Fuchsia 

 globosa each leaf-tooth is provided with a single terminal pore (in some 

 of the dark colored varieties there are several), which resembles an 

 ordinary stoma (Fig. 93). Beneath the pore is a cavity, commonly filled 

 with water (Fig. 95, b), which, by evaporation, deposits calcium car- 

 bonate upon the walls of the lining cells, thereby discoloring them. A 

 fibre-vascular bundle is continued from the veins of the leaf through 



* In '' Vergleichende Anatomie der Vegetation sorgane," etc., 1877, 

 on page 54, et seq. References are there given to the literature of the 

 subject, which is both recent and limited. After Mettenius' paper in 

 Filices Jiorti Lipsiensis, others appeared by other writers in Botanische 

 Zeitung, 18G9, 1870, and 1871. 



