CRYPTOBIOTIC STAGES IN BIOLOGY 5 



cultures of pathogenic streptococci from lyophilized prepara- 

 tions that have been stored under an inert gas at room tempera- 

 ture for nineteen years. 



SEEDS 



It is by means of dormant seeds that nature provides a way of 

 continuing the existence of many plant species. There are two 

 types of these^o. One, a seed that remains dormant only as long 

 as it remains dry. The process of germination is set in motion as 

 soon as the seed comes in contact with moisture. The other type 

 is a seed that remains dormant even though it has absorbed all 

 the moisture that is needed. In this case, germination does not 

 proceed until some external trigger mechanism sets the process 

 in motion. 



The first represents a type of dehydrobiosis common to the 

 seeds of cultivated plants, such as the gi*ains and maize. These 

 seeds remain dormant during storage because they are kept dry. 

 There may be a short period of after-ripening between the time 

 they are harvested and the time they are planted, but in these 

 seeds this period is short and occurs during the normal period of 

 storage. When such seeds are planted, they imbibe moisture 

 rapidly and germinate in a few days. The wild parents from 

 which these cultivated plants have been derived probably did 

 not have seeds of this kind, but through a long period of 

 cultivation and natural selection, types have been developed 

 which produce seeds that do not require any special trigger 

 mechanism for germination. This is desirable in order that all 

 the planted seeds germinate at the same time to produce plants 

 that mature at about the same time. With seeds of this kind, 

 there is some difference of opinion as to whether or not they are 

 in a real state of cryptobiosis. In many studies on such seeds, it 

 would appear that a slow rate of respiration goes on during the 

 storage period even though the moisture content is low, and 

 that this rate of respiration increases as the moisture content is 

 increased^i. It is not certain, however, whether this respiratory 



References p. 13 



