EMBRYO, SEED AND CARPEL IN THE DATE. 143 



form 



changes which occur. 



Zone of Digestion. At first a spherical mass of intact cells 

 (a, figure 14a) this becomes differentiated into two zones 



due 



ed 



tein. We have therefore to note (1) the cause for the col- 

 lapsing of the cells which is found in the digestion of the 

 primary walls; (2) the disappearance of the contents, due 

 to the digestion of the oil and protein. 



Digestion of primary cell walls. Sachs (1862) believed 

 that the primary membrane is not digested during germina- 

 tion, but that the growing haustorium pushes the exhausted 

 and crushed cells before it. Reiss (1889) extended Sachs' 



osperm of Chamaerops humi 



I have 



found no evidence to the contrary after a stage ot germina- 

 tion roughly indicated by an embryo length of 2 cm., at 

 which stage the haustorium has attained the form of a 



sphere 

 tween my 



no lack of harmony be- 

 and those of Sachs and 



Reiss, which have been generally accepted. 



Newcombe (1899) extracted a ferment capable of digest- 

 ing the whole of the endosperm cell wall. This result is of 

 interest in that there is yet advanced no optical evidence 

 that the primary membrane is actually digested in the date. 

 Newcombe's results appear to indicate that there are two 

 ferments extractable together, 26 one capable of acting on the 

 primary wall, the other on the reserve cellulose. The former 

 may be present during germination in such small amounts 

 that the result of its action on the primary wall is inappre- 



d 



made 



act. Probability is lent to this interpretation by the work 



of Green. 



26 The contrary view that a single ferment isolated by Newcombe 

 is capable of digesting both primary walls and the reserve cellulose is 

 negatived by the positive evidence that such digestion does not take 

 place during germination; though the logical possibility remains that 

 it takes too long or that it is inhibited in some way. 



