SECT. I 



MORPHOLOGY 



01 



Centrioles and Centrosome-like structures in the lower divisions 

 of tlie Vegetable Kingdom (^^). — These appear as more or less 

 sharply defined portions of the cytoplasm, which are surrounded by 

 radiations. In the case of certain marine Algje (Fucus, Stypocmdon, 

 Fig. 5G) one or more small bodies, which may be compared to the 

 centrioles of animal cells, can be distinguished within them. Such 

 included bodies are wanting in the corresponding masses of active 

 cytoplasm in Fungi. We may relate these structures to specially 

 defined masses of cytoplasm in the mother-cells of the spermatozoids 

 of the Bryophyta, Pteridophyta, and certain Gymnosperms. These 

 are termed blepharoplasts and supply the material for the formation 

 of the cilia of the spermatozoids. 



The Chpomatophores (^'^). — In the embryonic cells of the embryo 

 and of growing points, where the chromatophores 

 (Fig. 55 ch) are principally located around the 

 nucleus, they first appear as small, colourless, 

 highly refractive bodies. They may retain the 

 same appearance in older cells (Fig. 121 A, I), but 

 in them they also attain a further development, 



as CHLOROPLASTS, LEUCOPLASTS, Or CHROMOPLASTS. 



Since these bodies have the same origin they are 

 all included in the one term, CHROMATOPHORES. 



Chlopoplasts. — In parts of plants which are 

 exposed to the light the chromatophores usually 

 develop into chlorophyll bodies or chloroplasts. 

 These are generally green granules of a somewhat 

 flattened ellipsoidal shape (Fig. 62), and are 

 scattered, in numbers, in the parietal cytoplasm 

 of the cells. All the chloroplasts in the Cormo- 

 phytes, and, for the most part also, in the green 

 Thallophy tes, have this form. In the lower Algae, 

 however, the chlorophyll bodies may assume a 

 band-like (Fig. 263 C'), stellate, or tabular shape. 



lu these cases the cliloroplast often includes one or more pyrenoids ; those are 

 spherical protoplasmic bodies containing an albuminous crystalloid, and are sur- 

 rounded by small grains of starch (Fig. 263, C 2^)- The chlorophyll grains are 

 said to be connected by special cytoplasmic filaments which allow of their changing 

 their position ; according to Bengt Lidfoiiss (•*"), these are kinoplasmic filaments, 

 while according to F. Knoll {^°) there is a special cytoplasmic reticulum. The whole 

 apparatus is connected by filaments with the nucleus. The ground substance of 

 the chlorophyll grains is itself colourless, but contains numerous coloured granules 

 which are termed grana. The pigments can be extracted by means of alcohol. A 

 strong solution of chlorophyll is most readily obtained from foliage leaves by the 

 use of hot alcohol. The pigments of chlorophyll are also soluble in acetone, ether, 

 and chloroform ; less completely in petrol-ether and petrol-benziue. The alcoholic 

 solution is bright green by transmitted light, while, owing to its fluorescence, it 

 is blood-red by reflected light. When an alcoholic solution of chlorophyll is 



Fig. 62. — Two cfills from a 

 leaf of Funaria hygro- 

 metrica. cl, Chloroplasts ; 

 n, nucleus, (x 3O0.) 



