iqiq] rose— AFTER-RIPENING AND GERMINATION 301 



(7) seeds remaining in contact with moist soil out of doors over 

 winter gave 77 per cent of germination the next spring; whether 

 this result is due to the low temperature, to certain constituents of 

 the soil, or to a combination of these or other factors one cannot say. 

 The results obtained by Kinzel (15), together with those just 

 summarized, show that as yet the conditions necessary for the 

 germination of Samhucus seeds are not fully determined. To 

 permit the water content of the seeds to fall below an undetermined 

 critical point may lessen their viabihty. However, that some other 

 condition or combination of conditions is responsible for the low 

 percentages of germination must not be overlooked. Kinzel's 

 suggestion that prolonged freezing is necessary should be given due 

 consideration. 



RUBUS 



Seed fruits of Ruhiis Idaeus, like the seeds of the 2 species already 

 discussed, fail to germinate when placed on a moist substratum. 

 It was determined that this is not due to an immature condition 

 of the embryo. If the pericarp is left intact all treatments with low 

 concentrations of acids, bases, and salts, immersion in warm water, 

 cold storage, exposure to increased oxygen pressure, or to ether 

 vapor, freezing and thawing, and injection with water under 

 pressure are ineffective. 



When buried in the soil at 15-20° C. or out of doors over winter, 

 a low percentage of germination takes place if the seeds are kept 

 moist. Two lots of 720 viable seeds buried for 140 days under 

 these conditions gave respectively 40 per cent and 20 per cent 

 germination. Of 2 similar lots of seeds buried in tightly stoppered 

 bottles, one at constant, the other at varying temperatures, none 

 germinated when planted in the soil in the greenhouse. That 

 these results are not due to injury resulting from drying or to 

 inability to absorb water is indicated in table XII. The removal 

 of the endocarp was accomplished by soaking the seeds in con- 

 centrated sulphuric acid for approximately 2 hours. Following this 

 treatment the seeds were washed quickly in a large amount of 

 running water to prevent heating, then immersed in a 5 per cent 

 solution of sodium bicarbonate to neutralize the remaining acid, 



