Minnesota Plant Life. 



519 



protruded which undergoes rapid divisions, growth and differ- 

 entiation, finally becoming a little green, prostrate, heart- 

 shaped body with abundant root hairs and leaf-green granules. 

 So, too, a fungus spore customarily protrudes, through a cleft 

 in its wall, its first pale thread that nourishes upon whatever 

 may be its proper food, ultimately divides, branches, grows and 

 brings into existence a new fungus body. The pollen spores 

 of flowering plants are not infrequently furnished with special 

 thin places in their walls, through which the tubular sporeling 

 may easily emerge. The necessary general conditions of ger- 

 mination are sufficient warmth and moisture and, in some in- 

 stances, the chemical stimulus of a proper food supply outside 

 the spore wall. 



Care of sporelings. In all plants more or less provision is 

 made for the protection and nourishment of the sporelings. 

 The spore commonly contains food material, or mechanism for 

 making it, and the supply of food is carefully adjusted to the 

 needs of the new plant. For this reason in smaller club- 

 mosses, quillworts and water-ferns the large spore is furnished 

 with a comparatively generous stock of provisions, in the form 

 of starch and aleurone grains, and consequently becomes as 

 large as a grain of sand. Unlike most spores, these are dis- 

 tinctly visible without magnification. In the plants mentioned, 

 the female, consisting of numerous cells, among which the egg 

 is of prime importance, does little or no independent vegetative 

 work, and must perforce have provisions enough reserved for 

 her use to enable her to reach maturity. Sporelings with spe- 

 cial necessities, such as pollen-tubes, have special food sub- 

 stances provided for them and are stimulated and directed in 

 their growth by structural adaptations of the tissues around 

 them and by chemical stimuli that guide them towards the eggs 

 of their species. 



Production of spermatozoids. All plants except the lowest 

 algae and fungi produce gametes, or fusing cells. In a few 

 lower algae the cells that fuse are alike, and in many fungi the 

 fusing cells become blended into one body, in which it is diffi- 

 cult to distinguish the male and female portions. In most of 

 the algae, in liverworts, mosses and ferns and in all the higher 

 plants there are undoubted distinct and dissimilar sperms and 

 eggs formed in special cells or organs. 



