330 NATURAL SCIENCE. 



July, 



The remaining lots, D, D% were similarly treated at the end of 

 the fourth day, when the roots were well developed, and the plumule 

 had attained a length of 5 mm. 



After drying, ten specimens were removed from each lot, put 

 aside in a dry place, and set to germinate five months afterwards (in 

 the following March). The results were quite analogous to those 

 obtained with the other seedlings. M. Bonnier found that all the 

 seedlings dried at 85° had quite lost their germinating power, except 

 twelve out of the forty comprising the lot A^ and these produced very 

 poor plants, of which eight ultimately perished. 



Of the seedlings dried at 35°, thirty-four out of forty of B, two 

 recovered, giving plants as vigorous as those produced normally from 

 seed. Of C, twenty-eight out of the forty recovered, but the resulting 

 plants were less vigorous than those from seed, and five ultimately 

 perished ; while of D, only twenty-one out of forty recovered, yielding 

 poor plants, twelve of which ultimately perished. No recovery took 

 place under the same conditions with plants further advanced. 



We see, therefore, that the recovery after drying depends on the 

 stage of development of the seedling, and also on the temperature at 

 which it is dried. It is very interesting to note the length of time — 

 several months — during which the state of suspended animation can 

 be retained. 



Beans germinated for eight to fifteen days at 14° C, and then dried, 

 for one day at 35°, were able to resume active life ; but if dried longer- 

 at the same temperature until there was no more loss of weight, they 

 did not recover. 



In the case of the haricot, younger seedlings must be taken than 

 with the bean to ensure recovery. On these M. Bonnier made some 

 histological observations. Seeds were germinated for two days and 

 then dried completely at 20°, 35°, 55°, and 85° respectively. On 

 examination of sections of the cotyledons in glycerine, the aspect of 

 the cells was very different in the different cases. As we should 

 expect, the dessiccation had a much greater effect on the protoplasm 

 than on the cell-membrane, or the starch or aleurone grains. In fact,, 

 in the seedling dried at 85° C, there was no sensible change in the 

 thickness of the last three ; but the grains were much more crowded- 

 against each other and the cell-wall by the shrinking of the proto- 

 plasm. Iodine has a similar effect on the starch grains in the seed- 

 lings dried at 20° C. or 85° C, while Zinc Chlor. Iodine or aniline 

 Violet colours the membranes almost in the same way. The proto- 

 plasm dried at 85° is very strongly stained by aniline-violet, but. 

 scarcely at all at 20° C. ; Carmine in water stains it immediately at 

 85° C, but not at all at 20° C. These simple tests, M. Bonnier 

 suggests, might be used to examine the power of germination by 

 means of reagents. It is evident that the water combined with or 

 contained in the protoplasm plays the most important part in the: 

 passage from active life to the dormant stage, and vice versa. 



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