1889.] Tubercles on the Roots of Leguminous Plants. 



431 



2.6 p.m. Whole region of solar plexus painted with nicotin sulph. 



2.10 „ Stim. splanchnic for 45 sec. Blood pressure remained at same level, 

 60 mm. Hg. In the tracing there were no respiratory variations, 

 hut at intervals of 25 to 30 see. there was a slight fall of the blood 

 pressure. 



IV. "On the Tubercles on the Roots of Leguminous Plants, 

 with special reference to the Pea and the Bean." By H. 

 Marshall Ward, M.A., F.R.S., F.L.S., late Fellow of 

 Christ's College, Cambridge, Professor of Botany in the 

 Forestry School, Royal Indian Engineering College, 

 Cooper's Hill. Received October 22, 1889. 



(Preliminary Paper.) 



In the 'Philosophical Transactions' for 1887 (vol. 178, B, pp. 

 539 — 562, PI. 32 and 33) I published the results of some investiga- 

 tions into the structure and nature of the tubercular swellings on the 

 roots of Vicia faba, the broad-bean of our gardens, paying attention 

 to the bearing of the facts on other Leguminous plants, and discussing 

 what had been done and written at various times concerning these 

 curious structures. 



The chief facts established in that paper were as follows : — That 

 the tubercles occur in all places and at all times on the roots of 

 Papilionaceous plants growing in the open land, hut that in sterilised 

 media and in properly conducted water-cultures they are not deve- 

 loped, unless the root is previously infected by contact with the 

 contents of other tubercles. In other words, the tubercles can be 

 produced at will by artificial infection. I also showed that the act of 

 infection is a perfectly definite one, and is due to the entrance into 

 the root-hair of a hypha-like infecting tube or filament, which 

 starts from a mere brilliant dot at the side or apex of the root-hair, 

 passes down the cavity of the latter, traverses the cortex of the root 

 from cell to cell, until its tip reaches the innermost cells of the cortex, 

 where it branches and stimulates these cells to divide and form the 

 young tubercle. 



It should be noted that these fruits of the infection were entirely 

 new, as were the methods, and that I showed actual preparations of 

 the infecting filaments passing down the root-hairs, to several 

 botanists at the time (June, 1887). 



In my paper were also explanations of several points hitherto 

 obscure — such as the curious trumpet-shaped enlargements of the 

 filaments where they transverse the cell-walls of the tissues, suggest- 

 ing that they were due to subsequent stretching of the walls of the 

 meristematic cells. Also the peculiar haustorium-like swellings of 



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