191.1] The Ottawa Naturalist. 159 



These were merely flat masses of eells, spread on moist soil. 

 Now came another ministry of progress. Neighboring plants 

 occupying the surrounding territory grow over a flat mass and 

 cut off its supply of light. Protoplasm responds to this danger 

 by breaking the flat expanse into irregular parts attached to a 

 central axis, and this axis soon rises slightly from the soil. This 

 is the condition we find in the mosses. But another danger is at 

 once encountered. Such elevated parts are removed from the 

 necessary water supply, although favorably placed for light and 

 air. 



So if elevation of parts is necessary there must be devised a 

 conducting system, and a strengthening system also, to enable 

 the erect plant to resist wind currents. Protoplasm recognizes 

 and meets this difficulty. Among the mosses we find a suggestion 

 of a stem the green surface is divided into somewhat regular 

 little leaflike parts, and these are placed radially on a short, 

 central axis, which is strong enough to hold them erect a fraction 

 of an inch. But no true conducting structures are met in plants 

 lower than the ferns. There we find that ordinary short roundish 

 cells become immensely elongated, and their side walls strength- 

 ened. The presence of these tubes, which permit a readv passage 

 of liquid from the soil to the uppermost parts, makes possible 

 what we have in our most complex groups of plants roots for 

 absorption deep in the soil, stems and leaves reaching mam- 

 yards above the soil. These tubes must be held erect against 

 gravity and the destructive rush of the wind. So wood is develop- 

 ed a mass of cells part of which are modified into tubes and 

 another part into fibres slender, strong and elastic. 



Let us now glance back for a moment and notice that some- 

 where in the advance from simplicity, there enters the phenome 

 non of Death, as we think of it. We saw that the simplest organ- 

 isms cannot be said to die, inasmuch as the living parent is 

 merged in the offspring of which it forms so considerable a part. 



But apparently as an associated condition with the evolution 

 of sex came the need of a certain maturitv of parent, and the 

 germ cells became at length not the whole of the parent but only 

 a small proportion of its mass. Then we find that the mature 

 plant produces germ cells only once, or a limited number of times, 

 and after such definite effort at reproduction, the parent dies, 

 except as represented by its offspring, to which it has contributed 

 a minute portion. This small contribution from the parent 

 carries with it a wonderful power of heredity, but not sufficient 

 to prevent variation, or to enable us to sav that the individualitv 

 of the offspring is lost. 



The fact of variation is undeniable, we mav find examples in 

 every family, and in the leaves of every tree. "The possibility of 



