32 
PLANT MORPHOLOGY. 
primary wall, or of the subsequent lamellae making 
up the walls of the cells of the pith, medullary rays, 
parenchyma and other tissues, or it may arise as an 
intercellular substance. 
The following is a classification of some plants, based 
upon the origin of the mucilage which they contain : 
1. Cell- Content Mucilage : 
Corm of Orchis sp. (salep); rhizome of Agropyrum repens -, 
bulb of Urginea maritima ; bulb of Allium sp. (onion, gar- 
lic); stem, leaf and elements of flower, excepting stamens, 
of Viola tricolor ; flower-stalks of Hagenia Abyssinica ; pulp 
of fruit of Musa paradisiaca (banana) ; succulent plants, as 
aloe, etc. 
2. Cell- Membrane Mudlage : 
a. Secondary thickening of wall: Root of Althsea officinalis; 
bark of Cinnamomum sp. ; bark of Rhamnus Frangula ; 
bark of root of Sassafras varifolium; inner bark of Ulmus 
fulva; leaves of Barosma betulina, and B. crenulala ; seed- 
coat of Cydonia vulgaris ; seed-coat of Linum usitatissi- 
mum ; seed-coat of Sinapis alba, and S. nigra. 
b. Metamorphosis of Cell wall : 
a. Pith and medullary ray cells; Astragalus sp., yielding 
tragacanth. 
p. Parenchyma cells of wood and bark ; cherry gum, 
yielded by some of the Amygdalaceae. 
7. Various cells of the bark; Acacia Senegal, yielding 
gum arabic. 
5. Primary wall as intercellular substance ; thallus of 
Chondrus crispus (Irish moss). 
o. Secreting Hairs ( Driizemoiten ): 
Leaf and calyx of Viola tricolor and leaves of Coffea Arabica 
(coffee) and of Prunus avium. 
The origin of mucilage may be satisfactorily studied 
in the fresh corm of salep and in the root of althtea — in 
the former as a cell-content mucilage, and in the latter 
as a cell wall mucilage. 
