Human Physiology. 



the ovaries of the plant, the fertilising pollen in the cells of the 

 anther or male organ. By a great variety of special contriv- 

 ances and vital movements, the pollen is brought in contact 

 with the stigma, where it is retained by a viscid secretion. It 

 sends a long slender tube according to the length of the style 

 to the ovary, where it is met by a similar tube from the germ 

 cell. They are drawn together by a mutual attraction ; a new 

 centre of vitality is formed which grows into an embryo. It' 

 anything were wanting to the wonder of this vital process, most 

 wonderful in all the forms of organic life, it is to be found in 

 the fact, that when hybrids are produced by the union of 

 different species, the mule offspring, as was proved by Dr. 

 Herbert, Dean of Manchester, resembles the male parent in 

 foliage and the female in flower. 



Richerand says the plant is a being whose existence is 

 limited to the phenomena of nutrition and reproduction; a 

 machine constructed of a multitude of vessels through which 

 the sap is filtered to be evaporated in the leaves. It shows, 

 especially in its flowers, which are its organs of generation, a 

 faint sensibility, a contractility by which its vessels contract 

 and dilate, sometimes acting visibly; the stamina, or male 

 organs, bow themselves over the female organs, or pistils, 

 shake upon the stigma their fertilising dust, then retire from it 

 and die with the flower, while the ovary lives on and produces 

 seed or fruit. 



The leaf is the most important organ of the plant, for it is 

 by its changes of form that all the organs of flowers and thence 

 fruit are produced. Leaves are composed of cells and bundles 

 of spiral vessels, with skin and pores. A section of a leaf 

 (Fig. 2), highly magnified, shows its structure. 



It is in the leaf of the plant that its nutritive matter is formed. 

 It is its lungs and stomach, its secreting and excreting organ. 

 Water, filtered through the spongioles at the extremities of the 

 rootlets, ascends the straight or spiral tubes to the leaf, carry- 



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