THE BACTEROIDS. 349 



sectional preparations, stained by a solution of equal parts of 

 fuchsine and methyl violet in i per cent, acetic acid. This 

 colours the plasmal contents and membrane of the nodule-cells 

 blue, the bacteria of the infection threads being stained red, whilst 

 the membrane of the latter remains uncoloured. It should be 

 mentioned, in conclusion, that these threads of capsuled bacterial 

 colonies are but rarely found in the nodules of lupins. 



The bacteria which have gained access now develop in the cells 

 of the bacteroidal tissue, and, finally, under the influence of the 

 surrounding protoplasm, become modified into involution forms 

 termed bacteroids, rich in albumin and no longer capable of re- 

 production. This morphological change is represented in Fig. 63, 



Fia. 63. Development of bacteria to bacteroids FIG. 64. Reticulated band of 



from the meristem of a root-nodule of Vicia bacteroids from the nodules 



sativa. Explanation in the text. of Vicia Faba. 



Magu. 700. (After Beyerinck.) Magn. 700. (After Beyerinck.) 



in an example taken from the nodule of Vicia sativa shown in 

 Fig. 60. 



A section cut near the lower extremity meets the youngest 

 meristem, where only long rods (u) in a high state of development 

 are to be seen. A little higher up, in older layers (v), the com- 

 mencement of branching is already discernible, and is found in a 

 more forward state in a still higher position (x). Finally, in a 

 section across the cells of the internal tissue of the nodule in the 

 direction y (Fig. 60), none but variously shaped bacteroids (?/) for 

 the most part united to form reticulated bands (shown in Fig. 64) 

 occur. After attaining this condition the bacteroids are soon dis- 

 solved by the surrounding cell plasma and disappear. However, 

 before this occurs, small globular vesicles of an unknown nature, 

 which, however, should not be regarded as endospores, not in- 

 frequently appear in the interior of this formation. Little can as 

 yet be said of the chemical composition of the contents of these 

 bacteroids. Micro-chemical reactions, however, indicate that the 



