80 ORGANOGRAPHY. 



action of diluted sulphuric acid, and diastase, a peculiar nitro- 

 V genoiis substance occurring in germinating seeds. Starch was 

 ■ formerly considered as peculiar to plants (see page 4), and its 

 presence therefore was regarded as an absolute distinctive mark 

 between them and animals. Of late years, however, a sub- 

 stance presenting the chemical reactions and general appearance 

 of starch has been found in some animal tissues. Such a dis- 

 tinctive character, therefore, can be no longer absolutely de- 

 pended upon. 



Starch occurs in two states, either in an amorphous condition, 

 f or in the form of distinctly defined granules. Its existence in 

 I an amorphous state has been detected by Schleiden in the bark 

 I of the Jamaica Sarsaparilla, in the seeds of Cardamomuon minus, 

 and in the underground stem of Carex are7iaria ; also by Currey 

 and Tulasne in certain Fungi ; and by Schenck in Ornithogalum 

 nuta7is and 0. lanceolatum. Starch commonly occurs in the 

 form of colourless transparent granules, varying in size ; which 

 are either distinct from each other as is generally the case {Jig. 

 52), or more or less combined so as to form compound granides 

 '' {fig- 57). When fully formed the granules are usually found float- 

 ing in the cell-sap, but in a young state each granule is attached 



Fig. 59. 



Fici. 57. Compound starch granules of West-India Arrow-root. After 



Schleiden. Fig. 58. Wheat starch : magnified 250 diameters. Fig. 



59. Rice starch : magnified 250 diameters. 



I at one point of its surface to the protoplasm or primordial 

 I utricle, from which structures, as will be presently seen, it is 

 believed to be developed. In form the granules are always 

 spherical or nearly so in their earliest condition. In some cases 

 this form is nearly maintained in their mature state, as in wheat 

 starch {Jig. 58), but the granules frequently assume other 

 forms, as ovate, elliptical, more or less irregular, club-shaped, 

 or angular (see figs. 53-59). Such forms arise from the un- 

 equal development of the sides of the granules, or from mutual 

 pressure, the same causes indeed which give rise in a great 

 measure to the varying forms of the cells in which they are 

 contained. Starch granules vary also extremely in size in dif- 

 ferent plants, and even in the same cell of any particular plant. 



