SEC'f. I 



MORPHOLOGY 



97 



Lastraea and Afhyrium (^^)) where fusion takes place between cells of 

 the prothallium or first generation. The product of fusion gives rise 

 to the true fern plant, the diploid generation, . 

 while the sexual organs of the prothallus are 

 functionless. 



Multiplication of the Chromatophores. — 

 This is accomplished by a direct division, as a 

 result of which, by a process of constriction, a 

 chromatophore becomes divided into nearly 

 equal halves. The stages of this division may fig. 103.— ciuoropiiyii grains 

 best be observed in the chloroplasts (Fig. 103). from the leaf of Funaria 



hygrometrica, resting;, and in 

 proces.s of division. Small in- 

 cluded starch grains are pre- 

 sent in the grains, (x 540.) 



B. Cell Fusions 



The connection of the living protoplasts 

 with one another is less complete in plants than in the animal body. 

 This is evident from the existence of the cell-wall which surrounds 

 the vegetable protoplast. Recent researches have, however, shown ('''^) 





*— 5'^:v- •■:-^, WvO^^L ■ ''^ jJ^ 





Fig. 104. — A cell from the cortex of the 

 Mistletoe {Viscum album) ; the protoplast 

 has been properly tl.\ed and stained and 

 the wall (m> swollen. The pit-membranes 

 (s) are traversed by connecting threads ; 

 ch, chlorojjlasts ; n, nucleus, (x 1000.) 



m 



(??- 





/ 





■'■ n f 





B 



;;^\ 



C 



Fig. 105. — A, A swollen portion of cell wall 

 from the endosperm of the Vegetable I\'ory 

 Palm (Phytelephas macrocnrjxi). At s, s, 

 simple pits filled with cytoplasm ; in the 

 intervening pit-membrane are fine connect- 

 ing threads(plasmodesms);j)Z, other threads 

 traversing the whole thickness of the wall. 

 (X 375.) B, The contents of two opposed 

 pits and the connecting threads of the pit- 

 membrane, (x 1500.) C, the opening of 

 a pit and the connecting threads of the 

 pit-membrane viewed from the surface. 

 (X 1500.) 



that the protoplasts of the plant are united together by extremely 

 fine cytoplasmic filaments, which proceed from the boundary layer 

 of the cytoplasm and are known as plasmodesms. Such filaments 

 are mostly confined to the pit-membrane (Fig. 104), but may also 



H 



