ELM STEM 95 



The cases of the Elm and Linseed are examples of mucilage 

 derived from cell-walls ; but mucilage also makes its appearance 

 at times in the protoplasm : as an example may be taken the tuber 

 of Orchis. Cut transverse sections of the tuber of 0. maculata 

 latifolia, or mascula, stain with corallin-soda and mount in 

 glycerine ; large cells will be seen in the parenchyma, with 

 mucilaginous contents stained pink, surrounding a central bundle 

 of raphides. 



Secretion of mucilage, in the first instance as distinct drops 

 within the protoplasm may be observed in the hairs which cover 

 the young parts of Blechnum and Osmunda. 



4. The sclerenchyma consists of cells with walls 

 so thickened that the cell-cavity is often obliterated : 

 the walls are differentiated into two or more strata. 

 Reactions with aniline sulphate, light yellow ; with 

 chlor-zinc-iodine, brownish red. 



5. The soft bast is, as in the Sunflower, composed 

 of several different thin-walled tissue-elements, which 

 are, however, difficult to distinguish in transverse 

 sections : they are 



a. Sieve-tubes, which are nearly circular in 

 section, and usually of larger cavity than the other 

 constituents. 



6. Bast-parenchyma : cells often arranged in more 

 or less regular radial rows : certain of the cells differ 

 from the rest in containing one or more crystals. 



The nature of these several tissues will be more 

 successfully studied in longitudinal sections. 



6. The cambium consists of thin-walled cells ar- 

 ranged, as in the Sunflower, in radial rows, which may 

 often be traced outwards into the phloem, and inwards 

 into the xylem : the cells have .copious protoplasm, in 

 which an elongated nucleus may often be observed. 



