BOTANICAL SUBJECTS. 179 



All such teratological cases as are quoted in the Appendix tend 

 to incline me to look upon the tendrils of cucurbits rather in the 

 way of aerial roots than in that of stipules. In wild forms, no 

 doubt, heredity keeps them single, and on the side of the leaf, but 

 in the garden forms, heredity being disturbed by crossing, varia- 

 tions are often produced, which " let the cat out of the bag," so to 

 speak, and give us a clearer conception of the homology of certain 

 organs. In my ^dew, however, aerial and ground roots, branches, 

 leaves, and stipules are all either branches or branchlets, so that 

 the morphologist has an " embarras de choix." 



The point is to find out which parts are the nearest relatives. 

 In the case of cucurbits, it would seem the tenckil is nearer the 

 aerial root than the stipule. 



We have now to examine the roots of another large group of 

 plants, the Leguminiferee. 



What are the tubercles which are so common a feature on the 

 roots of this group of plants ? 



In "Xature" of 25th December 1890, p. 189, there is a 

 notice of certain " Field experiments at Rothamstead," conducted 

 by Sir John Lawes. It is there stated that " In recent years the 

 question of assimilation of free nitrogen by grooving plants has 



assumed quite a new aspect The results of exjjeri- 



ments made by Hellreigel and Wilforth, so far obtained, show that 

 when a soil grooving leguminous plants is infected with appro- 

 priate micro-organisms, there is a development of the so-called 

 leguminous nodules on the roots of the plants, and coincidently, 



increased growth and gain of nitrogen There is 



no evidence that the leguminous plant itself assimilates free 

 nitrogen." 



The reviewer hastens to label this micro-organism as a fungus 

 of the " class UstilagincE, which exists in and is the cause of the 

 tubercles, or root nodules, found upon the root-fibres of leguminous 

 plants." 



Are we to understand by this that all leguminous plants do 

 not assimilate nitrogen without the help of these micro-organisms ? 

 Are we also to understand that these organisms are the sole 

 originators of these tubercles ? 



Surely there are other plants which contain nitrogen in their 

 composition. The seeds of grasses, and the alcaloids of many 



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