1917] CURRENT LITERATURE 161 





transpiring power and usually low maximum index values. In addition to the 

 transpiration data, this paper contains a description of an improved apparatus 

 for providing a standard evaporating surface.— Geo. D. Fuller. 



Fossil cycads. — The second volume of Wieland's 22 memoir on American 



fossil cycads represents a large amount of additional work on material with 



* structure preserved, and in particular of a new monocarpic trunk from the 



Black Hills discovered by Dr. N. H. Darton. It is replete with admirable 

 line drawings and half-tones representing both external form and internal 

 structure. The material is in addition illustrated by 58 superb plates in helio- 

 ! gravure. The whole constitutes an achievement of which American paleo- 



botany may well be proud. 



Although the volume is described as systematic in its contents, it con- 

 j tains much that is of interest to the anatomist and the evolutionist. Con- 



siderable space is devoted to the anatomy of trunks of cycadeoidean forms, 

 and the fact that the fibrovascular tissues are much more woody than in the 

 I living representatives of the cycads is emphasized. This is the consequence 



of the narrow rays and the sparse parenchyma, both features of contrast to the 

 living cycadean cylinders. The author apparently has not found in American 

 Mesozoic material the interesting reduplication of the central cylinder recently 

 described by Stopes in a publication of the British Museum. This situation is 

 interesting as it tends to discredit the hypothesis of Worsdell that the redu- 



plication of the cylinder in cycads is a vestige of the complex system of fibro- 

 vascular bundles found in certain species of Medullosa, etc. The situation in 

 fact is comparable rather with that found in vines, and it is interesting to note 

 in this connection that it is not improbable that the cycadeoidean genus 

 Anomozamites was a climbing plant. The author emphasizes the statement 

 that the mucilage cavities of the cycadeoidean forms were isolated cysts and 

 did not constitute a system of canals as in living cycads. 



Certain interesting statements are recorded in regard to the leaves, although 

 most of these represent only elaborations of facts already known. The leaf 

 trace departs from the cylinder as a large horseshoe-shaped strand which passes 

 directly toward the leaf base, breaking up into numerous bundles in transit. 

 This situation is in marked contrast to conditions in the living genera where 

 numerous strands take their exit from the cylinder for each leaf and pursue a 

 circuitous course through the cortex toward the leaf base. It is obvious that 

 the cycadeoidean forms, so far as their anatomy is known, were unilacunar, 

 that is, there was a single gap in the cylinder of the stem for each foliar supply; 

 while in the living Cycadales the vascular system of the leaf is multilacunar. 

 The cycadeoidean condition is obviously more primitive, as it is found in the 

 reproductive axis and occasionally in the seedling of living forms. The ana- 



22 Wieland 



Carnegie Inst. 



Washington, Publication 34. 19 16. 



