490 Minnesota Plant Life. 



constituted an independent green organism. So, too, do many 

 humus plants, such as coralroots and pine-saps, depend upon 

 the presence, in their underground portions, of root-fungi. By 

 aid of these they can secure from the soil organic substances 

 that alone they could not collect. In return for such service 

 they harbor the fungus in their tissues. 



Intra-specific partnerships. Among higher plants a remark- 

 able division of labor exists. By it the spore-bearing plants of 

 the species exist as the primary food-gatherers, while the egg- 

 producing and sperm-producing plants live dependently upon 

 them, having no original food-collecting capacity of their own. 

 Thus, among flowering plants the female, quite devoid of leaf- 

 green, lives upon substances stored up for her use in the rudi- 

 mentary seed borne by the spore-producing plant. The 

 male, also, among flowering plants, lives parasitically upon the 

 tissues of the immature seed or fruit. Similar conditions are 

 known to exist among certain ferns and club-mosses. Other 

 highly interesting inter-relations for nutrition are those between 

 the mother plant and the offspring, as in cone-bearing trees; 

 or between the twin embryos in seeds of higher flowering plants. 

 In the latter instance one of the twins customarily gorges itself 

 with food for the benefit of the other, and by the latter it is 

 ultimately devoured. In such a life-history as that of the sun- 

 flower, for example, only the ordinary green leaf-bearing plant 

 of the species is an independent collector of food. Upon it 

 depend the male and female plants, the albumen-plant of the 

 seed, and, for a time, the embryo-plant that is later to develop 

 into a new leaf-bearing individual. 



Storage of food. After absorbing its food materials from 

 the air, soil, water or bodies of other organisms, these are re- 

 combined by the plant into characteristic products. In green 

 plants the first visible product of assimilation is starch. This 

 substance originates in the leaves and other green portions 

 under the influence of sunlight. It arises as little white gran- 

 ules. These may grow to a considerable size, but are ordi- 

 narily attacked by ferments, converted into soluble sugars and 

 conveyed along the conduction-paths of the plant either to 

 growing areas where they are used in construction, or to storage 

 areas, such as bulbs, tubers, fleshy roots, seed-albumen or bud- 



