I.] 



MILK, FIBRES, VEGETABLE ORGANISMS. 



103 



11. Vegetable Cells forming a Membrane. With a pair of 

 forceps peel off a thin layer of the covering of a fresh onion bulb. 

 Examine it either in. water or in water after staining with a solution 

 of iodine (H). Observe the cells (fig. 57) with well-defined walls, 



X 



Fro. 57. Cells from bulb of a fresh onion forming a membrane. M, cell membrane ; 

 N, nucleus seen from the surface; Nn, nucleolus; V, vacuoles, x 240. 



and united to each other by the edges to form a membrane the 

 exeentrically placed spherical nucleus and the granular ccll-con- 

 tents. 



12. Cells with sinuous margins, and containing chlorophyll 

 granules, may be studied in a leaf of the Duckweed or Lemna minor, 

 also the reaction for cellulose (sulphuric acid and then tincture of 

 iodine = blue) in the same plant. - 



13. The currents in protoplasm are well seen (H) in CJiam ml- 

 '/a/v'x, which is so common in our streams. 



Vegetable Micro- Organisms. These are frequently found in 

 microscopic preparations, while others are the cause of various 

 diseases. They are usually classified as follows: 



1. Mouldy 



2. Saccharomi/cetes (yeast-like organisms). 



3. Schizomycetes (bacteria-like organisms). 



14. Penicillium (H). This mould is readily found on starch- 

 paste or on Mailer's fluid preparations which have been left stand- 



