BOTANY. 339 



bio.«is with legiiminons or otlier plants. Amnionlacal nitrogen 'is readily assimilated 

 by the lower orders of phmts without the intervention of sunlight, but in the higher 

 j>lants the assimilation, while taking place in darkness, is much more active in the 

 light. Nitric nitrogen is assimilated by the lower organisms in darkness, but among 

 green plants with few exceptions the assimilation of nitrates is most rapid when the 

 plants are exjiosed to the light and particularly in the more refrangible rays of the 

 spectrum. Whenever free nitrogen, ammonia, or nitric nitrogen are assimilated in 

 darkness there is a considerable consumption on the part of the plant of carbo- 

 hydrates, W'hich furnish the necessary energy for the reduction and synthesis (^f the 

 albuminoids. 



The lower plants in general are able to synthesize albuminoids in the dark, l)ut in 

 higher plants, as a rule, this takes place only in the light. Among the higher })lants 

 amid bodies in limited quantity are produced in portions of the plants which are free 

 from chlorophyll, as in the instance of germinating seeds in darkness. There does 

 not seem to be any transformation of nitric acid or ammonia in a full-grown flower- 

 ing plant except that taking place in the sunlight. 



The influence of light and darkness upon growth and development, D. T. 

 MacDougal {3h'm. New York Bot. Gard., 2 {1903), -pp. XIII ^ 319, figs. 176; ahs. in 

 Bot. CenthL, 93 {1903), No. 14, pp. 296, 297). — After summarizing the. previous inves- 

 tigations on the effect of light and darkness on the growth of plants, the author gives 

 the results of his own experiments with over 100 species, representing many orders of 

 plants. The etiolated condition of the leaves of different plants, the effect of darkness 

 on flowers and inflorescences, and the effect on spores and sporangia of ferns are 

 described. In discussing the theories of etiolation and the effects of light and dark- 

 ness, the author says that etiolation is not an adaptation to darkness, and that the 

 forms which plants assume in the dark are not governed by an effort to reach the 

 light. 



The various phenomena of etiolation are, in the first instance, due to the mere 

 absence of light, and subsequent modifications appear which may be regarded as 

 beneficial to the plant, but at times may prove disadvantageous. The comparison 

 of normal and etiolated plants shows that growth and differentiation are not only 

 inilependent phenomena, but are easily separable. Light acts as a stimulating influ- 

 ence in inducing morphological differentiation, but it is not necessarily direct in its 

 action, since the stimulative influence may be received by one portion of the plant 

 and transmitted to another. The impulse may often be communicated to organs 

 which are not actually formed at the time of the stimulation. 



The amount of growth or increase in volume that may be accomplished l)y the 

 extension of the imperfectly developed tissues in the absence of illumination is sub- 

 ject to great variation. In many instances the total length, diameter, and volume of 

 the etiolated shoot may be less than that of a normal one, while in other instances it 

 may be decidedly greater. The author states that there is no evidence afforded by 

 the behavior of plants in darkness to warrant the conclusion that light directly affects 

 the rate of growth. A bibliography of more than 200 references accompanies the 

 work. 



The influence of a lack of oxygen on plants, M. Dude {Flora, 92 {1903), p. 

 20.5; ahs. in Bot. CenthL, 93 {1903), No. 27, p. /<S').— The effect of a lack of oxygen on 

 various seeds and spores was investigated. It was found that keeping seed in an 

 atmosphere free from oxygen resulted in their ultimate death. 



Quite a number of species of seed were kept in an oxygen-free chamber for a con- 

 siderable time and samples were tested from day to day for their vitality. Rye lost 

 its germinative ability after 50 days' exposure, peas after 43 days, sunflowers 40 days, 

 vetches 35 days, and white mustard 15 days. In every case germination was retarded. 

 Where the seed and spores were kept free from oxygen for only 5 days their germi- 

 nation was considerably retarded and the subsequent growth was entirely abnormal. 



11776— No. 4—03 3 



