Minnesota Plant Life. 



157 



much reduced in size. When an egg lying at the bottom of the 

 organ which produced it has been fecundated, it segments by 

 partition-walls. One of the first two cells develops into the 

 embryo. Some of the cells later produced form the first leaf 

 of the embryo plant. Another group forms the apex of the 

 stem, and still another matures into a bulbous body which nurses 

 upon the tissues of the sexual plant ; while, much later, from the 

 interior of a root-like elongation a group of cells pushes its way 

 out as the first true root. 



In all the higher plants roots seem to have originated from 

 inner portions of the plant-body and may be regarded as being 

 everywhere protrusions of the sap-conducting areas, so that the 

 root is essentially an absorbent tract, while its functions of sup- 

 port are secondary. 



The embryo plant thus started on its career continues to 

 grow, thickening its stem, forming new leaves and branches and 

 multiplying its roots. Unlike the moss capsular plant, but like 

 the capsular plant of the horned liverwort, it never of its own 

 accord stops growing, but only when the growth is terminated 

 by outward unfavorable conditions. As it grows and branches 

 year by year, it soon becomes strong enough to form spore- 

 producing areas of its own. 



In club-mosses the spores are in little pouches, one on the 

 upper side of each leaf on the cone-shaped tip of some branch. 

 The end of the branch which produces spores becomes cov- 

 ered with leaves, sometimes of a different color, drier and paler 

 than the ordinary foliage leaves. Such cones are equivalent 

 to the cones of pine-trees which are supposed, indeed, to have 

 arisen from similar simple types. Each cone consists of an 

 axis clothed with spore-bearing leaves. Since the latter in most 

 club-mosses are specialized to some extent for their reproduc- 

 tive functions, they progressively abandon the starch-making 

 function ; hence, not needing illumination, they stand closer to- 

 gether, overlapping each other as they would not do if depend- 

 ent upon the sunlight for leaf-green energy. Having taken 

 such positions they become bleached and while the general 

 plant-body of a club-moss is provided with green, unbranched, 

 rather needle-shaped leaves, the cones by their yellow color and 

 flatter and more closely crowded leaves, become distinct areas 

 of the plant. Yet in types of club-mosses lower than the ordi- 



