32 COMPENDIUM OF GENERAL BOTANY. 



Laminaria, the gummy exudation from Astragalus gummifer, seeds 

 of 'Linum, Gummi arabicum from the bark of Acacia Senegal, and 

 other species, roots and leaves of Althaece, and the gelatin of marine 

 algae. The membranes of entire cell-complexes often become 

 mucilaginous (tragacanth gum). What has been stated in regard 

 to the mucilage of orchid-bulbs indicates that mucilage may be 

 produced within the cell, hence is not always of membranous 

 origin. 1 



(d) Yarious coloring materials are deposited in cell-walls of 

 different plants : santalin in red sandalwood, haematoxylin in the 

 blue campeche-wood, brasiliri in red-wood, morin in yellow- 

 wood, etc. In all these cases, as also in the well-known ebony 

 (Diospyros Ebenum\ we are concerned with a transition from phloem 

 (Splint) into heart-wood (kernholz) ; or in other words a deposition 

 of coloring substances -and tannin in the originally colorless cellulose 

 membrane. Cell-walls containing silica and carbonate of lime have 

 been known for a long time ; the former among Equisetce and 

 Graminece. Burning such silica-bearing plants after treating with 

 sulphuric acid leaves a "skeleton." This skeleton consists not only 

 of SiO 2 , but usually also of salts of K, Ca, and Mg. The silicious 

 membranes of the small cells in the epidermis of many grasses 

 (dwarf-cells) serve as a protection against destruction by snails 

 (STAHL). Incrustation of cell-walls with calcium carbonate has been 

 observed in the hair-cells of phanerogams (Composite, Borraginece) ; 

 calcium oxalate occurs in cell-walls of conifers. Those peculiar 

 excrescences of the cell-wall extending into the cell-lumen (Ficus, 

 Acanthacece) containing calcium carbonate and known as " cysto- 

 liths " also belong here. According to HABERLANDT the calcium 

 carbonate contained in the cystoliths of Ficus Carica (leaf) is ulti- 

 mately redissolved and utilized in the metabolic processes of the 

 plant. 



C. PRODUCTS OF THE GROWTH IN THICKNESS AND SURFACE OF 

 THE CELL-WALLS. 



We must distinguish the uniform growth in surface and thick- 

 ness of the cell-walls from the not less frequent and especially im- 

 portant localised growth. We have already touched upon that 



FRANK'S Physiologic gives a more detailed summary. 



