ion of Angiosperms! Germination. VII. 



GERMINATION: The renewal of normal active mftahnltsm on the pan of 

 the resting embryo ('gtrm ' of older writers) ; hence also applied to the active growth 

 from a spore, and even from a personating structure, as 



Dependent on physical environment, in terms of tamptrsnra, uypn ssuly, 

 prater-supply; three essentials all requisite, implying normally *tB ssr and, dsisp 

 and warm soil, as characteristic habitat of a land-plant; in case of very hard seeds 



also dependent on the permeability of the testa-layers. 



Water taken up by imbibition of colloidal cell- membranes, leads to imbibition by 

 colloidal plasma, and osmotic activity soon implies turgidity of all living units. Food- 

 supplies for kataboUsm and growth are requisite before the photosrntbetic rmrnansiBl 

 can get to work; hence the more food on hand the better; ad insoluble u serves 

 require to be made soluble before they can be conducted. This is effected by the 

 action of enzymes also liberated by addition of water to the plasms, 



BniymM are proieids with catalytic activities, hydrolyzing or oxidative, 

 chemical change : living plasma is its own catalyst, but enzymes secreted by 

 may be active outside the cell producing them, and may be brought to bear on n 

 (as a massive starch-grain) not in immediate contact with living! plasma. Different 

 classes distinguished according to material acted on, as (i) DM t tost, hydrolyzing 

 starch to sugars (including invcrtase); (a) Cykut, hydrolyzing ruerva osldosss to 

 sugars ; (3) Lipau, hydrolyzing and oxidizing fais, to sugars in pan ; (4) /Vtfstsr 

 breaking down proieids to ami no -acids, etc. Different enzymes in different seeds 

 according to reserves, and often produced in special cells ; e. g. enzymes of embryo 

 may be secreted into endosperm-tissue (largely inactive), rendering its reserves rapidly 

 soluble. 



Fatty Reserves : the general case, stored in embryo or endosperm ; fat rapidly 

 disappears, much free oxygen being used up in the process : cf. palm-oil of EUtu 

 kernels, used for margarine : glyceride of palmitic acid, originally of glycerine and 

 3 chains of palmitic acid, each 16 C atoms, with separation of 3H,O : first hydrolysed 

 back to glycerine and the free acid ; the latter oxidized in part, and broken up to sugar 

 groups, etc., cf. full structural formula. 



Starch Reserves: good example in the malting of barley, for maltose (mak> 

 sugar, disaccharide) : cf. Zta Mais. Main mass of endosperm packed solid tfh 

 starch ; embryo at basal end, with radicle in sheath (coleorhiza), plumule with first 

 sheath leaf (coleoptile), cotyledon, one only as tcuttllum, an absorbing organ with 

 V.B., lying in contact with the endosperm as a broad shield-like tract of parenr v - 

 with superficial layer of columnar cells ('palisade'): the latter secrete an 

 diastase into the floury endosperm ; the polygonal starch-grains, on testing with 

 show corroded spots and lines (white on the blue grain), and the grains break to 

 fragments and dissolve, giving soluble dextrins (polysaccharid e\ maltose (disaccharide). 

 and ultimately by maltase to dextrose (monosaccharide). The 

 absorbed by the scutellum cells, and passed on to the V.B. : 

 cope with the supply, transitory starch-grains are seen in sc 

 not in the palisade-cells. NoU that the peripheral layer of the endosperm, digestive 

 in the growing seed, stores no starch but aleurone-grains with globoids of phosphate. 



Emergence of the Embryo : The radicle, as important for continued auto- 

 absorption of fluid, emerges first ; the lip is normally pushed out at the micropyle by 

 elongation of zone ii, and if incorrectly orientated the latter adds a geotropic curva- 

 ture (positive). Further elongation of the A#<x-a/)7-region normally draws out the 

 cotyledons, and this region puts in a geotropic curvature (negative), if not previously 

 erected, pushing the cots, above the soil. The latter diverge (normally s in DICOL 

 type), and the plumule continues the further development of the shoot-system. 



Nott, for penetration of soil by root-apex some resistance is requisite, hence 

 necessity of the weight of a certain amount of soil; if msuffirimt the seed may be 

 lifted above ground ; well-developed cotyledons commonly carry up the old seed- 

 coats. The hypocolyl is neither stem nor root ; its vascular system links up the 

 stelar organization derived from two opposite growing-points. Intercalary eisrmioo 

 of this hypocot) Icdonary axis is utilized in normal ff*gc*l germination with photo- 

 synthetic cotyledons. 



15 



