58 



BOTANY 



very small. Tschirch has calculated that out of a square metre of green foliage 

 leaves only from 0"1 to P 2 grams of chlorophyll can be obtained. Acids decompose 

 chlorophyll ; contact even with the acid cell sap is sufficient to change the colour 

 of the chlorophyll bodies to a brownish green. It is due to this fact that a plant 

 turns brown when dried. 



The green colour of the chlorophyll in some groups of Algae is 

 more or less masked by other pigments. In addition to the chlorophyll 

 green, with its accompanying yellow and orange-red pigments, many of 

 the blue -green Schizophyeeae contain a blue colouring matter, phyco- 

 cyanin ; the brown Algae, a brown pigment called phycophtein ; while 

 the red Algae possess a red pigment termed phycoerythrin. These 



:g. 57. — Cell from the 

 upper surface of the 

 calyx of Tropaeohtm 

 majus, showing chroma- 

 tophores. ( x 540.) 



Chromoplasts of 

 the Carrot, some with 

 eh grains. ( x 540.) 



n 



Fig. 58.— Cell from the red pericarp 

 of the fruit of Crataegus eoeeinea, 

 •it, Nucleus, (x 540.) 



pigments, which are peculiar to Algae, are soluble in water, and are 

 characterised by a beautiful fluorescence. The phycocyanin may often 

 be found as a blue border surrounding a blue-green Fission-Alga 

 which has been dried in a press. Red seaweeds washed up by the 

 ocean soon become green, as, owing to the rapid decomposition of the 

 phycoerythrin, the chlorophyll is no longer concealed. 



Before leaves fall in the autumn, their cells lose almost all of 

 their cytoplasmic contents, and at the same time the chloroplasts 

 undergo disorganisation. There remains only a watery substance in 

 the cell cavity, in which a few oil globules and crystals, together 

 with a few yellow, strongly refractive bodies, can be seen. Sometimes 

 this liquid in the cell cavities becomes red, and thus imparts to the 



