STARCH. 53 



tain algae the chlorophyll-body itself contains other coloring matters- 

 soluble in water, however in addition to the chlorophyll. In Floridecs 

 (red sea-weeds) this extra coloring-matter is red ; in Fucacece, brown ; 

 in Diatomacem, yellowish ; and in Oscillatorm, blue. 



In the degradation of chlorophyll, which takes place in the walls of 

 the antheridia of mosses, and in the ripening of some fruits of Phanero- 

 gams, other colors than green are produced. 



(/) Plants which live parasitical ly upon others, as the Dodder, and 

 those which are saprophytic in habit, as some fungi, are usually desti- 

 tute of chlorophyll ; where the parasitism is only partial, as in Castttleia 

 and Gerardia, or where the food used (stolen) by the parasite is unaa- 

 similated, as in the Mistletoe, chlorophyll is present. In the true para- 

 sites (found mainly among the fuugi) chlorophyll is never present. 



(g) The colors of flowers are produced in various ways. In some 

 cases rounded masses, apparently protoplasmic iu their nature, contain 

 a red (e.g., Adonis), orange (e.g. , Zinnia), or yellow (e.g. , Cucurbita) color- 

 ing-matter. In other cases the pigment is dissolved iu the watery fluid 

 of the cells ; blue and violet colors are mostly produced in this way. 

 White petals are so because their external layers of cells are filled 

 with air. An important difference beween chlorophyll and the pigments 

 of flowers, is that the latter appear not to be dependent upon light for 

 their production ; this may be shown by enclosing branches of morning- 

 glory (Ipom&d) bearing young flower-buds in a dark chamber ; when 

 the flowers expand they will be seen to have their natural colors. 



II. STARCH. 



67. Next to chlorophyll, one of the most important pro- 

 ducts of the plant-cell is starch, an organic compound closely 

 related to sugar and cellulose, and represented by the em- 

 pirical formula C 12 H ao 10 . It occurs in the form of whitish 

 or semi-transparent, rounded or slightly angular stratified 

 grains, and is generally found closely packed in the interior 

 of certain cells. 



68. The form of starch grains varies greatly in different 

 plants, and considerably even in the same plants ; neverthe- 

 less, the general appearance of the grains in each plant is so 

 characteristic that the different kinds of starch may be quite 

 easily distinguished. In every case the grains have more or 

 less clearly defined lines, which are concentrically arranged 

 about a nucleus * (Figs. 44 and 45). In some cases (excep- 



* The nucleus is called the hilum by some authors, a term which 



