EPIDERMIS. 



T05 



The epidermis of the under side of the leaf of Ficus elastica has similar, but 

 smaller and more scattered cystolilhs. The same structures have been proved to 

 exist in all other species of Ficus which have been investigated on this point, the 

 form and size varying according to the species. The cystolith-cell has in other 

 species a much broader outer wall at the surface of the epidermis than that in Ficus 

 elastica (e. g. F, australis, salicifolia), or its thick outer wall itself rises as a more or 

 less long hair-like apex above the latter (Ficus Carica, montana, ulmifolia). 



Other Urticaceae have similar cystolith-cells, and cystoliths in the epidermis : 

 species of Parietaria, Boehmeria, Forskahlia tenacissima, Celtis, INIorus, Broussonnetia, 

 Humulus, Cannabis, Conocephalus, Urtica (Payen). A form differing from the round 

 or oval is shown by the bodies in question in Pilea decora, densiflora ? (Weddell), 

 Urtica macrophylla (Fig. 45). The cystolith is here spindle-shaped, straight or with 

 two curved legs (Pilea densiflora ?), it lies in a cell of form similar to itself, of which 

 the greatest diameter is parallel to the epidermal surface, and it is attached to the 

 middle of the outer wall of the cell by a stalk, which arises from the middle of one 

 side of it. The structure of the spindle-shaped cystoliths is the same as that of the 

 round ones. In the Urticace^e the cystoliths are absent in Ulmus and Dorstenia 

 (Payen). 



Fig. 45.— Urtica macrophylla; piece of the epidermis with cystolith-cells, from the upper side of the leaf; 



transverse section (225). 



The cystoliths of the Acanthaceae, w-hich w-ere first found by Gottsche (in 

 Schacht, /. <:.), resemble in structure those of the Urticacese : their form is seldom 

 round (Justicia carnea, Schacht), usually spindle-shaped, or like a transversely 

 halved spindle. Their attachment by a stalk is also often similar to that above de- 

 scribed (Justicia carnea, Beloperone oblongata, Schacht, /. c.) : but the half-spindle- 

 shaped ones are attached by a very thin short stalk, arising at a point of their trun- 

 cated end, to a lateral wall of the, cell which conceals them. Schacht describes 

 cystoliths in the epidermis of the above Acanthaceae, further of Barleria alba, Ruellia 

 formosa, livida, Justicia paniculata, to which Eranthemum pulchellum, Goldfussia 

 anisophylla, and others should be added. He *ailed however in finding them in 

 Justicia purpurascens and Acanthus mollis. 



On the occurrence of cystoliths in the sub-epidermal tissue in Urticaceae and 

 Acanthaceae, see sect. 32. 



' The knobs which surround the base of the hairs in the Borraginacese, and many 

 Synantherae^, are allied to the cystoHths of the nettle-Hke plants.' The base of these 

 hairs, which is embedded in the epidermis, is surrounded by one or two concentric ring- 

 shaped rows of cells which are distinguished by their wall, on the whole surface facing 

 the hair, being covered with a well-marked stratified thickening, which protrudes inwards 



' Von Mohl, Botan. Zeitg. 18&1, p. 229. 



