84 WAX, BLOOM, ETC. [CH. 



is a good example, where the wax is so abundant that it 

 is excreted on to the surface in the form of granules, or 

 of rodlets perpendicular to the surface, and forms a layer 

 which can be rubbed off with the fingers. If organs of 

 this kind are plunged into water while the wax layer is 

 intact, they are not wetted, but glisten as if covered with 

 silver, owing to the layer of air entangled between the 

 water and the wax ; and if rain-drops fall on the surface 

 they roll off at once with a silver reflexion suggesting the 

 utility of the bloom for preventing lodgement over the 

 stomata. That the waxy bloom is also a protection 

 against parasitic fungi is also a tenable hypothesis. In 

 some cases, such as the nodes of the Sugar Cane and 

 other Grasses, the leaves and stems of some Palms 

 (Ceroxylon klopstockia), various fruits (Myrica cerifera), 

 &c., the wax layers are several millimetres thick and can 

 be utilized in commerce by scraping off and separating 

 the wax in hot water. 



In other cases fatty or resin-like substances are 

 secreted in the cuticle e.g. leaves of Gymnogramme, 

 and certain viscid buds to be referred to below. 



The epidermis itself presents all the ordinary features 

 of a cell-tissue, and its cell-walls and contents may show 

 all the peculiarities of those of typical cells. Nevertheless, 

 in the majority of cases certain characters of general 

 application are to be noticed, as follows. As a rule the 

 epidermal cells only divide by walls perpendicular to the 

 surface of the young organ, and consequently the layer is 

 only one cell thick : exceptions are not common, but they 

 do occur e.g. Mistletoe, Ficus, Begonia, and others. 



Again, the rule is that the ordinary epidermis-cells, 

 although living and provided with normal protoplasmic 

 contents and nuclei, do not contain chlorophyll-cor- 

 puscles : the exceptions chiefly concern certain shade- 



