1909] 



CURRENT LITERATURE 249 



cotyledon. The cotyledonarv bundles contain either centripetal xylem or its 

 lineal descendant, transfusion tissue, the pronounced mesarch bundle occurring 

 in greater proportion in the Taxineae (Taxus and Cephalotaxus) . With respect 

 to the number of cotyledons, only members of the Pinaceae (Cryptomena and 

 Sequoia gigantea in the Taxodineae, and Libocedrus and some species of Cupres- 

 sus among the Cupressineae) have more than two. The presence of resin ducts, 

 likewise, was observed only in the Pinaceae, Juniperus having them in the leaves, 

 and the Taxodineae having them in the cotyledons in all the forms examined, 

 except Widdringtonia. Two instances of fusion of cotyledons are reported: in 



rm 



the leaf of Sciadopitys; in Cupressus torulosa, the cotyledons fuse near the base 

 form a tube. In every case the number of root poles corresponds with the 



number of " whole " cotyledons. .. , 



The authors believe that dicotyledony is the more primitive condition, and 



J "' . - i-.i- K,,f the 



form 



statement of their reasons for this conclusion is deferred to a future paper. 



It is a hopeful sign that the authors did not intrust this valuable collection 

 of seedlings to the mercy of a razor; to read that the sections were made in an 

 orderiy fashion with the help of a microtome gives double assurance that the obser- 

 vations are accurate. — Helen A. Dorety. 



Root excretions.— Stoklasa and Ernst 12 report a conclusive piece of work 



The excellent technique these workers have developed in 



potass: 



- V/H.H.IIU1KI, J. lie CA^CllClil lCV,illH4LH- i."v.-«- ■ , fiplH 



handling similar problems makes their contribution in this much disputed 

 unusually valuable. They find that no acid (organic or inorganic) except H , 3 

 is excreted by roots, if they are fully supplied with oxygen, so that aerobic respi 

 tion is unrestrained. In limited oxygen supply, certain organic acids are o^ 

 «ad excreted; but in no case is any inorganic acid or salt excreted; not even **»> 

 ' im phosphate, contrary to the claim of Czapek. The organic acids a P F 

 » -der limited oxygen supply vary with the plant used. Buck* e 

 barley gi ve formic and acetic acids; oats and maize, formic; and the Deei, - ■ 

 Stoklasa and Ernst believe these acids arise from the incompletely o 

 Products of respiration. In a full oxygen supply they maintain that tnese 

 «* oxidized to carbon dioxid and water. whether 



The authors are to make an exhaustive investigation of the questio 

 ^ hydrogen is produced in the aerobic respiration of roots, an d what °^ 

 a °ds are excreted by the roots of many other species of plants under limited oxy g 



Supply. 



The authors also determined the amount of CO . excreted by the root systems 

 of Parley, oats, rye, and wheat. The barley root-system gives off m g 

 to*unt of CO, and produces the greatest dry weight. The quotient arising 



12 



Stoklasa, t and Ernst, A., Beitrage ziir Losung 



\ j J *' ^knst, A., u enrage /.m ^~- — o 



Ur des Wurzelsekretes. Jahrb. Wiss. Bot. 4 6:55-^ 2 - l 9 cS ' 



