194 Spratt . — A Comparative Account of the 
nodules of Phaseolus and Coronilla ; Peirce has described them in Trifolium ; 
the writer has frequently observed them in young nodules. The nucleus 
in the young bacteroidal cells is well defined, with a prominent nucleolus, 
but as the cell increases in size it becomes associated with a large central 
vacuole. In Lotus corniculatus frequently two nucleoli are present, and in 
Coronilla the nucleus becomes amoeboid and subsequently divides so that 
many cells are multinucleate. 
Many of these plants have a very wide distribution and show an 
immense adaptation to their environment, e. g. Trifolium and Lotus . They 
live principally on poor dry sandy soil like the plants of the Genisteae type, 
and like them produce characteristic tannin sacs, styloids, and oblique 
medullary rays. Styloids are especially prominent in the outer tissue of the 
nodule of Phaseolus (see PL XIII, Fig. 9). These nodules all have one 
vascular strand at the base and may be grouped thus : 
(a) Phaseolus , Coronilla , and others where the vascular strand divides 
at the base below the bacteroidal tissue into four strands, which supply the 
nodule for some time before any further branching occurs. 
(b) Ononis , Anthyllis , and others in which the vascular strand divides 
at the base into two. 
(e) Trifolium , Lotus , and others where the single strand passes from 
the base obliquely to one side of the nodule and remains undivided for 
some time ; later it branches, but at some distance from the base. 
III. In the Viceae type the nodules have an elongated form with 
a well-defined apical meristem and a basal intercalary zone which produces 
a small amount of tissue. The nodule frequently branches and may form 
very large clusters, e. g. Vida Faba and Stizolobium ; but there is one 
continuous bacteroidal zone, the apical portions of which are traversed 
by innumerable infection threads. In young nodules these threads are 
distributed throughout the whole tissue, but later they are confined to 
the areas where new cells are continually being formed and infected with 
Bacillus radicicola . The nuclei, which are at first large and prominent, 
lose their spherical outline, become elongated and irregular, and eventually 
separate into two or more irregular granular bodies associated with a large 
vacuole, and later become further dispersed (see PI. XIII, Fig. 10). Two 
vascular strands are produced at a very early stage of the development of 
the nodule on opposite sides, each of which has a separate attachment to 
the root-stele (see PI. XIII, Fig. 7). 
In this group are a large number of plants of considerable agricultural 
value which require a moderately good soil with sufficient clay to keep 
it moist and calcium carbonate to prevent acidity. The genera Vicia i 
Pisurn, Lathy ms , Galega , Stizolobium , and Colutea have been examined 
and found to have nodules of this type. 
IV. The nodules of the above groups all occur on annual plants or are 
