EXTRACT XXIV. 



ON LIGNIFICATION IN PLANTS AS COMPARED WITH 

 OSSIFICATION IN THE HUMAN ORGANISM. 



LIGNIFICATION, or the consolidation of vegetable tissue, 

 seems to have something in common with, ossification, 

 or the consolidation of animal tissue. Thus, as ossifi- 

 cation consists primarily of the invasion of certain struc- 

 tural areas of the nascent organism by earthy salts, the 

 union of these with the structural elements of those areas, 

 the hardening organisation, and ultimate consolidation, of 

 them, on definite skeletal lines, and, so, ultimately, the 

 conferring on the soft structures of a power, to attach 

 themselves to the resistant skeleton, and become, through 

 it, an articulate and moving, organism : so is lignification 

 a hardening organisation and ultimate consolidation of 

 vegetable protoplasm, by its union with earthy matter, in 

 definite fibro-cellular lines, along the stem, branches and 

 leaves, of the plant or tree. In the latter process we see 

 pretty much the same method of the union, or consolida- 

 tion, of the protoplasm, and earthy elements, in the 

 tissues of the plant, as we witness in the bodies of the 

 vertebrae, through the instrumentality of the notochord 

 the " pith," with the medullary rays, acting as the 

 vehicle of transference, from the soil, to the protoplasmic 

 cambium of the plant of the earthy elements, by which the 

 ligneous tissue becomes fully evolved, as a permanent 

 structure. 



This necessitates two circulations, the one, passing up 

 the stem, inside its bark, the elements of vegetable proto- 

 plasm, while the other transmits, by way of the pith 



