A text-book of mycology and plant pathology . ut yetsmaller are the ultramicroscopic organisms, which have come intoprominence recently as the cause of certain diseases. The smallestbacteria stand at the borderline of what is with the best lenses andoptimum illumination the practical limit of microscopic vision. Onthe other hand, with the application of the ultraviolet light of shortwave length in microphotography, it has been possible to obtain animage of small objects whose- enlargement has been 4000-fold. Ithas been possible with the ultramicroscope of Siedentopf and Zsig- 21 22 MYCOLOGY mo
A text-book of mycology and plant pathology . ut yetsmaller are the ultramicroscopic organisms, which have come intoprominence recently as the cause of certain diseases. The smallestbacteria stand at the borderline of what is with the best lenses andoptimum illumination the practical limit of microscopic vision. Onthe other hand, with the application of the ultraviolet light of shortwave length in microphotography, it has been possible to obtain animage of small objects whose- enlargement has been 4000-fold. Ithas been possible with the ultramicroscope of Siedentopf and Zsig- 21 22 MYCOLOGY mondy to demonstrate small particles whose size is only many milliontimes that of a milHmeter. The accompanying tigure (Fig. 4) adoptedfrom Fuhrmann^ represents the relative size of the spheric bacteriaand the rod-shaped organisms, while the breadth of the largest knownbacterial cell, that of Beggiatoa mirabilis, which approaches that of ahuman hair in thickness, is represented in the larger area where thewidth of the cell is twice its Fig. 4-—Diagram representing the relative sizes of spheric and rod-shaped bacteria{After Fuhrmann.) Diame ter in m I. Micrococcus progrediens 0. IS SphericBacteria 2. Micrococcus urea I to 1-5 3- Sarcina maxima 4- 0 [ 4. Thiophysa volutans 7 toLength in m 18 Breadth in ii 5- Pscudomonas indigojera 6. Bacillus influenza 7- Methane bacillus 50 Rod-shaped 8. Urobacillus Duclauxii 2 to ID to Bacteria 9. Bacillus nilri 3 to 8 2 to 3 10. Beggiatoa alba 2 .9 to 5 .8 2 .8 to 2 . Q II. Chromatium Oheni 10 to 15 5° ^ 12. Beggiatoa mirabilis 10 to 20 I. S to The cells exhibit a definite cell wall which differs from that of thehigher plants in not containing cellulose. The chemical character ofthe cell membrane indicates its close relationship to the living proto-plasm of the cell. Chitin has been found in the cell wall of somebacteria. Frequently the cell membrane undergoes a mucilaginousmodification, so that the
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Keywords: ., bookcentury1900, bookdecade1910, bookidtextbook, booksubjectfungi
