CARBON MONOXIDE AND OTHER GASES 61 
the average length of the several roots. As to the branching of 
the roots and the unrolling of the leaves, what was said about the 
wheat applies here. 
In considering the secondary members both of the root and of 
the shoot, it may be said in general that the seedlings in gas and 
CO presented a very imperfect development. Branches of the 
shoot were only observed in V7cta and while the control showed 
such branches frequently the others did not. Secondary roots 
were observed in all cases, however, and it was found that in CO 
and gas the formation of the regular root-system was greatly re- 
tarded if not inhibited. In the latter secondary branches were few 
and poorly developed, while the controls would have a healthily 
developed system. In gas especially the roots often appeared 
sickly, more so indeed than the shoots. In the corn, while the 
normal root-system was far from being completely formed in CO 
Or in gas, an interesting exception was seen as to the production 
of lateral members, which as has been said are usually fewer in 
these cases than in the normal. Below the circle of adventitious 
roots ordinarily developed in corn seedlings a considerable number 
of supernumerary secondary roots arose without order and grew 
out for a millimeter or two. 
In connection with this may be introduced a description of 
the peculiar thickening noticed at the base of the stem of many 
of the seedlings grown in CO or in gas. In Vicza for instance 
the normal diameter of the base of the stem next the seed 
being 3.5 mm., the CO specimens were 4.5 mm., and those in 
gas were 5.0 mm. in diameter. Melianthus, Fagopyrum and 
Stnapis also showed a similar but less well-marked thickening, 
and the curious enlargement of the leaf-sheath in the wheat and 
rice seedlings has already been referred to. In corn, however, the 
difference in size of the stem-base is most conspicuous and seems 
to be connected with the formation of the supernumerary roots just 
spoken of. The corn is the only form that has so far been exam- 
ined microscopically and the anatomical conditions are briefly as 
follows. The cells of the cortical parenchyma are greatly en- 
larged, though apparently no more in number. In the plants 
grown in CO these cells measure from one third to one half more 
in diameter than do those of the control, while in the gas speci- 
