VABIOUS STARCHES. 19 



represents such a compound grain of medium size. The indi- 

 vidual component grains appear polygonal, separated from one 

 another by clear-looking boundary lines. 

 Amongst the great grains are seen small 

 ones, also compound, down to such as con- 

 sist of but two component grains ; lastly, 

 also, quite simple ones, and besides these 



also numerous angular grains (#), which A B 



arise from the breaking down of the large FIG. 8. Oat starch from 

 compound grains in making the prepara- ^^ jj > ~_ 

 tion. Amongst compound grains, a certain P nent g ( x 540). 

 medium size, somewhere about our Fig. 8 A, is met with by far the 

 most commonly. Lamination is not visible in this object; the 

 hiluin is only indicated in exceptional cases. 



Starch Grains of Euphorbia. Of altogether peculiar appear- 

 ance are the starch grains in the latex (milk) of the Euphorbiaceae. 

 A piece of the fresh stem of a spurge is cut off and the cut surface 

 is immersed in a drop of water which we have ready upon the 

 object-slide ; the latex which flows out from the cut surface 

 mingles with the drop. We can, for example, select for study 

 a very widely-spread garden weed, the sun-spurge (Euphorbia 

 helioscopia). In the latex, which appears distributed in the water 

 as small drops, like an emulsion, we shall see isolated small rod- 

 like bodies (Fig. 9). These are the starch grains in question. 

 They appear pretty strongly refractive ; lami- 

 nation is indicated only in the most 

 favourable cases ; sometimes a longitudinal 

 cleft is recognisable in the interior of the 

 grain. The size of the rods varies some- 

 what ; many of them are slightly swollen in 

 the middle. Much more beautifully-formed 



grains of this kind are found in tropical 



_ . . FIG. 9. Starch grains 



Euphorbias, -b or examination we can cnoose from the latex ofEupkwUa 



Euphorbia splendens, or E. Jacquinaflora ^>**>/^ ( x 540). 

 (preferably the former), both of which are commonly grown in plant 

 houses for the sake of the brilliant scarlet bracts surrounding the 

 inflorescence ; and make the preparation in the same way as stated 

 above. The starch grains which we now see (Fig. 10) are generally 

 in the form of bones, with slightly enlarged ends : others may be 

 shaped like rods, and still others have greatly enlarged ends, like 

 dumb-bells, and in the swollen parts often permit something of 



