7 2 



SCIEXCE-GOSSIP. 



quently absorbed by the leguminous 

 plant. 



(3) It may be that this nitrogen assimilation 



is a "powerful act of machinery on the 

 part of the leguminous plant " which is 

 stimulated to such unwonted activity by 

 the organisms living in its root-nodules. 



(4) Lastly, it may be that the nitrates elsewhere 



produced are simply gathered together by 

 the root-organisms which are then, so to 

 speak, devoured by the higher plant. 



The first hypothesis depends chiefly for its 

 support upon Professor Frank. It seems, in truth, 

 to revive the old question, which, as already 

 mentioned, was long ago believed to be decided by 

 the work of Boussingault and others. 



The second suggestion, which is due to Berthelot, 

 perhaps brings with it the greatest plausibility. 

 "Whether it is a real factor or no, remains, of course, 

 still undecided. It may very probably be that 

 there are several causes constantlyat work "fixing " 

 the nitrogen of the atmosphere, but a consideration 

 of Berthelot's experiments and of the inferences he 

 draws from these, certainly gives colour to the idea 

 that one of these is to be found in the organisms of 

 the soil and roots, which, in the course of their vital 

 activities, oxidise the nitrogen of the air which then 

 finds its way into the higher plant. 



Professor Hellriegel, who was the first to notice 

 the root-nodules and their inhabitants and to 

 connect them with the nitrogen supply of the 

 leguminous plant, has gone further than this, and 

 has also attempted to explain the manner in which 

 the organisms of the root act. He says that these 

 bacteriads do not themselves bring about the 

 fixation of nitrogen, but that they act upon then- 

 host plant, s ti mulating its cells to unusual activity. 

 The result of this increased vitality is shown in the 

 direct assimilation of atmospheric nitrogen by the 

 living cells of the sub-aerial parts. To anyone 

 unacquainted with the unlooked-for responses which ' 

 protoplasm frequently gives to stimulation, this 

 theory may appear extravagant. But in the light 

 of other facts connected with the so-called 

 phenomena of irritability this view is one deserving 

 careful attention. The last of the above-mentioned 

 hypotheses is also by no means an improbable one. 

 There can be little doubt that there are numbers 

 of non-living agencies which fix small and much- 

 scattered quantities of nitrogen, and it may be that 

 the bacteriads simply draw together and concentrate 

 this widely-spread store which then becomes avail- 

 able to the host plant. Still it must be admitted 

 that it is very doubtful whether the nitrogen, 

 " fixed" by inanima te causes, is sufficient to meet 

 the large demand made unceasingly by the 

 vegetation covering the face of the earth. 



A fact which should be borne in mind in all these 

 enquiries is that, of all parts of the plant, the 



nodules seem to be richest in nitrogen compounds. 

 Whether these are formed here, or whether they 

 occur simply as reserve substances, is apparently 

 the undetermined point. However these nitroge- 

 nous substances originate in the cells of the 

 tuberosities, they are utilised by other portions 

 of the plant by the breaking down or absorption 

 of the cells of the nodule. This conclusion has 

 been particularly emphasised in the mind of the 

 present writer by the observation that so many of 

 the nodules have certain areas of the otherwise 

 active cells undergoing dissolution and apparently 

 absorption by the other tissues of the plant. Such 

 a " corroded " area is shown in fig. 2. 



Little need be said concerning the anatomy of 

 the nodules, this can be gathered from the sketch 

 given in fig. 3. On the extreme outside of the 

 tuberosity there are corky cells, within this the 

 living cells of the cortex, then are to be noticed the 

 fibro -vascular bundles (three are shown in the 

 figure), and within the ring of these again comes the 

 pith which forms the main mass of the root-swelling. 

 A few cells of this pith have been drawn under 

 high powers in fig. 4. The most noticeable point 

 in these cells is their evident protoplasmic contents 

 and large shining nuclei, both of which facts are 

 evidences of extremely active vitality, which we 

 may well suppose to be in some way connected 

 with the " fixing " of the free nitrogen of the air by 

 :he leg-.:— --c-3 plan: 



That the bacteriads of the root are of the utmost 

 use to the higher plant is evident from the above 

 considerations, but there is very good reason for 

 thinking that the benefit is not altogether one- 

 sided. It would seem, partly by analogy with 

 experiments made by Kossowitsch and others on 

 Algae, partly on other grounds, that whilst the 

 bacteriads furnish or aid in furnishing the 

 leguminous plant with nitrogenous materials, the 

 ;7re- z'.zs.: ;- ::; :ur- p — viles :he ~i:r;-:r;S.-:5~ 

 with the equally necessary carbo-hydrate food, 

 such as sugar, starch, etc. The relationship, there- 

 fore, between the lower and higher plants is one of 

 sy— i:;sis :r :;~ ~r-5a.l:;~ , 



Elmieood, BickUy, Kent; March T&th, 1895. 



Death of Professor J. D. Dana. — Professor 

 James Dwight Dana died of heart disease very 

 suddenly on April 15th, in his 83rd year. Born at 

 Utica, New York, he was educated in that State, 

 graduating at Yale College. Professor Dana was 

 most versatile in his scientific knowledge, and the 

 subjects of his numerous writings range from 

 v:lcs."e= "-- ~i ~ ; - ~ i--:e :cra.l= Kis grea: 

 works, by which he holds world-wide reputation, 

 are " Descriptive Mineralogy," now in sixth edition, 

 of over 1,000 pages; " Manual of Geology," in its 

 fourth edition ; and other standard works on corals 

 and zoophiles. Dr. Dana was a great traveller, and 

 investigated natural phenomena in many parts of 

 tie v.irli. 



