GERMINATION 225 



slowly. As regards further reactions of aleur one-grains 

 see Appendix B. 



VII. Crystalloids. Crystalloids of cubical form 

 are to be found in the superficial tissues of the Potato. 

 Cut tangential sections from material hardened in 

 alcohol, or in picric acid and alcohol, and mount 

 in pure glycerine and iodine : the cubical crystalloids 

 will be distinguished by their yellowish brown staining. 



Treat a section, in which one or more crystalloids 

 are under observation, with potash : the crystalloids 

 will be seen to swell and dissolve. 



Mount another section in alcohol or in glycerine, 

 and, having observed the crystalloids, irrigate with a 

 saturated solution of common salt : this also will dis- 

 solve the crystalloids. 



GERMINATION. 



(A) Dicotyledons. 



(a) Examine seedlings of Helianthus which ha ve 

 been germinating for different periods from one day 

 to one week, and observe the following points in the 

 process of germination : 



1. The internal parts of the fruit swell, and cause 

 the brittle pericarp to split longitudinally. 



2. The radicle protrudes, and curves downwards. 



3. The hypocotyledonary stem elongates, so that 

 the pericarp and seed-coat are carried upwards by the 

 cotyledons, which remain inclosed by them for a 

 considerable time. 



4. The coats of the fruit fall from the cotyledons, 



Q 



