B8 



BOTANY 



TAET I 



Fig. 72. — Chlorophyll 



The egg becomes capable of development as the result of fertilisa- 

 tion, although there are exceptional cases in the organic kingdom, 

 especially among the Arthropods, where an unfertilised egg may produce 

 an embryo. This is called parthenogenesis. In the vegetable 

 kingdom the existence of parthenogenesis in plants with advanced 

 sexual differentiation has only been proved in the case of C'hara crinita, 

 one of the Characeae. 



Multiplication of the Chromatophores. — This is accomplished by 

 a direct division, as a result of which, by a pro- 

 cess of constriction, a chromatophore becomes 

 divided into two nearly equal halves. The 

 stages of this division may best be observed in 

 the chloroplasts (Fig. 72). 



Inclusions of the Protoplasm — Starch. — 



The chloroplasts in plants exposed to the light 



almost always contain starch grains. These 



grains from the leaf of grains of starch found in the chloroplasts are the 



Funaria hygnmetrica, fi rst v j s ible products of the assimilation of in- 

 resting, and in process . * r™ „ - . _ 



of division, (x 540.) organic matter. lhey are formed in large 

 numbers, but as they are continually dissolving, 

 always remain small. Large starch grains are found only in the 

 reservoirs of reserve material, where starch is formed from the de- 

 posited products of previous 

 assimilation. Such starch is 

 termed RESERVE starch, in 

 contrast to the assimilation 

 starch formed in the chloro- 

 plasts. All starch used for 

 economic purposes is reserve 

 starch. The starch grains stored 

 as reserve material in potatoes 

 are comparatively large, attain- 

 ing an average size of P 09 mm. 

 As shown in the adjoining 

 figure (Fig. 73), they are plainly 

 stratified. Their stratification 

 is due to the varying densi- 

 ties of fhe successive layers. 

 They are eccentric in structure, 

 as the organic centre, about 

 which the different layers are 

 laid down, does not corre- 

 spond with the centre of the grain. The starch grains of the 

 legumes and cereals, on the other hand, are concentric and the 

 nucleus of their formation is in the centre of the orain The 

 starch grains of the Bean, Phaseolus vulgaris (Fig. 74), have the shaDe 



Fig. 73.— Starch grains from a potato. A, simple; 

 B, half-compound; C and D, compound starch 

 grains ; c, organic centre of the starch grains, or 

 nucleus of their formation. ( x 540.) 



