144 



PHYSIOLOGICAL BOTANY. 



how endowed with a new instinct, immediately becomes a new 

 centre of growth. First it expands to a proper cell, attached to 

 the wall of the sac near the micropyle. It then, by division and 

 subdivision, multiplies itself, and begins to 

 take form according to the species, showing 

 cotyledon, plumule, etc., until fully devel- 

 oped into the embryo (523). 



453. In the case of the CONIFERS (Pines, Cedars, Firs), 

 v here no styles or stigmas exist, the pollen falls directly into 

 the micropyle of the naked 

 ovule, and its tubes settle into 

 the tissue of the nucleus. 



451. Germina- 

 tion. The ovule ma- 

 tures with the comple- 

 tion of the embryo, 

 and passes into the 

 fixed state of the seed 

 in which the embryo 

 sleeps. A store of nu- 

 tritive matter. Starch. 522, Ovule of Viola tricolor, showing the process of fertilization 

 7 according to the views of Schleiden-^, pollen; <, tube; r, raphe; 

 fllltPTl PtC i c thoilO'llt- *%chfawa; b, primine; a. secundine; , nucleus; a, sac, wnich 



en, eic., i^ ^ he tube appears have penetr ^ t?d - 523 ' Grovvth of ? the ' enibryo 



522 



523 



fully provided in the 



seed for the use of the apexof 



young plant in germination, until its root has gained fast hold 



of the soil. 



455. The changes which occur in the seed at the recommence- 

 ment of growth, are simply such as are requisite to reduce its 

 dry insoluble deposits to a solution which shall contain the 

 proper materials for cell-formation or growth. Gluten and other 

 nitrogenous matters, oil, starch, etc., are to be changed to dias- 

 tase, the same as yeast ; and dextrine, the same as gum and grape 

 sugar. 



45G. To this end water and oxygen are absorbed; the gluten 

 begins decomposition, forming yeast ; fermentation ensues ; heat 

 is produced by the slow combustion of the carbon with oxygen, 

 forming and evolving carbonic acid, by which process some of 

 the oil and starch is destroyed, while another portion gains water 

 and turns to sugar; all this within the cells of the seed. 



