110 EXPEEIMENT STATION KECOED. 



dioxid. An apparatus was devised l\v which air free from carhon 

 dioxid could he supplied to one bell jar, and to another an atmosphere 

 containing approxiuiately 2 per cent of carbon dioxid. B3" means of 

 an aspirator the atmosphere was constantly changed. The plants used 

 were Marchantia lyolymorphi^ Lumdaria vulgaris, Luphvwi alhus^ 

 PJuiseolus midtiflorus, Faha wilgaris, Pisum sativum, Asparagus offici- 

 nalis, CucuThita p€p>o, Borrago officinalis, and Datura stramonmrn. 



The morphology of thallus, stem, and leaves is fully described. In 

 the case of the hepatics, the thallus was less developed, less branched, 

 and no asexual reproductive organs were produced when grown in an 

 atmosphere free from carbon dioxid. The assimilative tissues, usually 

 present in the large air cavities, were wholly absent in the case of Mar- 

 chantia and greatly reduced in Lunularia. The air spaces were like- 

 wise either wholly or nearly obliterated. 



Where plants were cultivated from seed, the stems for a time grew 

 best in an atmosphere which did not contain carbon dioxid, the pres- 

 ence of that gas retarding the consumption of the reserve material. 

 However, after the plant had used up its reserves and chlorophyll 

 assimilation begun, the best growth was obtained in an atmosphere 

 containing carbon dioxid. Those plants which were not cultivated 

 from seed, but were already in an advanced stage of growth, did not 

 show the preliminary phase just described, but continued their growth 

 best in the atmosphere charged with carbon dioxid. The leaves of the 

 plants were smaller when grown without carbon dioxid. In the case 

 of the Datura leaves, those already formed, when placed in an atmos- 

 phere lacking in carbon dioxid, became 3'ellow and fell oil'. In nearly 

 every case the leaves were thicker and the palisade parenchyma longer 

 and larger, the air spaces more developed, with all plants which grew 

 in the atmosphere charged with carbon dioxid. The internodes in 

 general section were larger, the number of fibro-vascular bundles 

 greater, and the individual bundles developed to a greater extent. 



The influence of different kinds of light on the form and struc- 

 ture of plants, E. Teodoresco {Ann. Sci. Nat. Bot., 8. ser., 10(1899), 

 jVos. 3-4., pp. 14.1-256; 5-6, pp. 257-264, pis. U,figs. 20).—\\\ order to 

 study the effect of rays of different refrangibility on the form and 

 structure of plants, the author made use of the spectrum and colored 

 screens, the colors used being red, blue, and green, and comparisons 

 were made with plants grown in light and darkness. The effect of 

 these different lights, as shown by the morphology and anatom}^ of leaf, 

 stem, and root, were studied, the experiments being described in detail. 

 The following plants were used: Horse beans, white lupines, buck- 

 wheat, castor beans, peony, evening primrose, Buhus fruticosus, live- 

 forever, peanut, vetch, white beans, pepper grass, chick-pea, gourd, 

 sunflower, hemp, horse-chestnut, potato, ash tree, maple, oak, and 

 syringa. 



