l62 



BOTANICAL GAZETTE 



[FEBRUARY 



tomical conditions in the Cycadophyta as regards the number of foliar gaps for 

 the vascular supply of the leaves illustrate the danger of using the number of 

 leaf gaps as a phylogenetic criterion, as has recently been attempted in the case 

 of the dicotyledons. The leaf supply of the cycadeoidean forms was dis- 

 tinguished from that in the petiole of existing cycads by the strong development 

 of secondary growth in the bundles on the upper side. 



The reproductive structures are considered in some detail in the light of 

 additional facts. The reviewer, however, expresses a regret, which will doubt- 

 less be common to those interested in the evolutionary history of the seed plants, 

 that so little further information has been secured in regard to the crucial 

 apical region of the seed. The author still maintains his earlier position in 

 regard to the cycadeoidean origin of the angiosperms. Although he is sup- 

 ported in this view by a number of eminent European paleobotanists, perhaps 

 it is open to question whether a hypothesis which finds little valid support in 

 the anatomical organization of either the reproductive or vegetative structures 

 will in the long run prove acceptable. The Goebelian character of the author's 

 morphology is everywhere apparent, but most strikingly perhaps when he 

 ventures to compare the seed of the Pteridosperm with an angiospermous 

 flower. Surely this is carrying the Goebelian definition of an organ as the tool 

 of a function to its logical reductio ad absurdum. 



The memoir under discussion contains a wealth of facts to which it is 

 impossible to do justice in a review. It will rank with those of Berry as a 

 most notable recent contribution to American mesozoic paleobotany. — 



E. C. Jeffrey. 





* 







< 





The cohesion theory. — The cohesion theory of sap ascent has received 

 much attention in recent years, and much supporting evidence has been 



brought out; 



Jost 2 3 



substantiated, and that all we need to do now is to find out w r here the cohering 

 water columns are located. He believes much experimental work is still neces- 

 sary to determine whether this theory is correct. Proceeding from early 

 experiments of Sachs and others, and using mainly such plants as Sanchezia, 

 Cobaea, Biota, and Chamaecyparis, he has made a quantitative study of water 

 delivery by the basal portion of decapitated plants, as compared with the 

 transpiration need of the top before and after cutting. The principal experi- 

 ments attempt to determine the influence of suction upon the rate of water 

 delivery by the root, and to determine whether continuous negative pressures 

 can be maintained by a transpiring plant. As suction and pressures of only 

 one or two atmospheres were used, the experiments seem to the reviewer little 

 adapted really to test the cohesion theory; and considerable space is occupied 



experiments 



23 J 0S t, Ludw 

 Bot. 8:1-55. 1916. 



Zeitschr 







