AGRICULTURAL BOTANY. 829 



detailetl account is f^iven <»f bis exiKTiiuciits wliicli were carried on witli •» 

 species of berltaccoiis plants and S species of trees. 



From the author's conclusions it appears that the jtroduction of dry matter by 

 green plants is determined l»y tlie eni-rtry of the light and varies with the illunii- 

 uation and tiie amount of chlorophyll in the leaves. The amount of cbbtrophyll 

 in a given plant varies from time to time, the nuninunu being associated with 

 full illumination in all the si)ecies studied. It increases rapidly with the dimi- 

 nution of illumination up to a maximum, after which there is a gradual 

 diminution if the light is still more reduced. In general the maximum of 

 chlorophyll production corresponds to an illumination considerably below that 

 which induces the formation of the maximmn dry weight of plants. The pro- 

 duction of dry matter in ]ilants increases with the increased light absorbed ui) 

 to a certain iioint, after which it decreases with accompanied greater illumina- 

 tion. The oi)tinunn of energy absorbed for a given plant is constant for a given 

 temperature, but diminishes when the temperature is increased. 



The optimum intensity of light for the production of dry matter varies accord- 

 ing to tlie quantity of chloroi)hyll contained in the leaves. Under natural 

 conditions of light the maximum production of dry matter in plants poor in 

 chlorophyll takes place in full sunlight, while on the contrary, with those 

 si)ecies ridi in green coloring matter the maxinnini production of dry weight 

 corres|jonds to a considerable attenuation of light. In general the develojinient 

 of a plant following its illumination is in proportion to the dry matter produced. 

 The growth of the stem and roots seems antagonistic, for while the rate of 

 development of the stem increases with illumination, that of the roots decreases. 

 The development of the leaves is affected in a manner similar to that of the 

 roots. 



With few exceptions, transpiration does not appear to have an appreciable 

 effe<-t on the total dry matter produced. The proportion of dry to fresh weight 

 decreases with illumination, and the illumination appears to exert a specific 

 influence upon the water contained in a plant, irresjjective of transpiration. 



All plants seem to be able to regulate the absorbed light energy and to protect 

 themselves against the unfavorable influence of an excess of light. From a 

 biological standpoint, iilauts growing in mass are at au advantage regarding an 

 increa.se in dry matter, since they are able to secure a considerable reduction in 

 the amount of total illumination. 



The transpiration of evergreen plants, M. I'utiusi (Atti R. Arcad. Lined, 

 h'liiil. ri. Sci. Fix.. Mill, r \ut., :>. scr., 11 {VMS), I, No. 10, pp. GGl-CUU!).— 

 From a stu«ly made of a number of dicotyledonous plants with persistent foli- 

 age, tlie autlKU- found that among the Lauraceie the energy of transpiration has 

 a well-deflned p«'riod!city with a nnnimum stage during December and January, 

 when cold weather and a ndninnnn of illumination coincide, and an optinunn 

 in the sjiring of tlie yi'.ir, wlu-n vegetative growth is actively renewed and the 

 surrounding conditions an* favorable. The curve of transpiration then de- 

 creases through tlie summer's heat and drought, and at length reaches the 

 winter condition of minimum activity. 



With I'ersea, Oreodapline, and other plants the energy of transpiration is 

 highest during midsummer, but Is not always In proportion to the atmospheric 

 conditions which favor the phenomena of transpiration. With the return of 

 autumn rains, transpiration becomes Irregular but Anally reaches the level of 

 the early si>ring condition. 



The respiratory pigments of plants, W. I'am.adin illir. I)<tit. lUit. (IcsflL, 

 2lja (/.W.S), Ao. 2, i>i>. 12')-1.{2: Xtschi: I'lii/siol. Chrm., .5.7 {litOS), \o. 2, pp. 

 207-222; ahs. in Jour. Chriu. Soc. [IjOikIoh], .VJ (tUOS), No. 5'/7, //. pp. 'ilG. 

 ■'iH). — During the autolysis of germinating wheat, kept under clilorofonii 



