﻿CURRENT LITERATURE 



of branches, the alpha type and the beta type, are noted. The former are more 

 vigorous, and the latter slender and with a lacunar cortex. The author con- 

 nects these types with one another as part of the same individual, regarding 

 the slender ramifications as possibly adapted to aquatic conditions. The 

 organization of the vascular tissues is protostelic, characterized as exhibiting 

 a central core of small, entirely tracheary tissue surrounded by an envelope of 

 larger elements of the xylem. The author calls attention to the support 

 furnished by Rachiopteris for the hypothesis put forward by Bower, Potoxie, 

 and others, for the branchlike origin of the leaf in ferns and their allies. — E. C. 



The grass embryo— Sargant and Arber," studying seedlings, and 

 embryos of grasses at the dormant stage, find many variants within the family, 

 which can be satisfactorily accounted for by deriving them from a hypothetical 

 form. This imaginary form they designate as A', and the relationships of the 

 various embryos and seedlings are worked out with much ingenuity. The 

 reviewer believes that the problem of the actual relations of monocotyledons 

 to each other and also to the dicotyledons will not be solved by erecting a 

 hypothetical form, but that real progress can be made by a critical study of the 

 earlier stages of the embryo, extending from the fertilized egg to the dormant 

 stage of the embryo. A study of the literature of the subject shows how little 

 is actually known of early embryogeny in angiosperms.— W. J. G. Land. 



Medullary phloem.— A recent paper by Worsdell^ 8 is of considerable 

 interest because it involves the deliberate application of general anatomical 

 principles derived from the study of the gymnosperms, living and extinct, 

 to the elucidation of the anatomical structure of the dicotyledons. Its author, 

 as a result of a sojourn in South Africa, became possessed with a large amount 

 of material of the Cucurbitaceae, a group well developed in this geographic 

 region. He finds good reason for concluding from the study of the conservative 

 peduncular and petiolar regions that internal phloem, a feature of the family, is 

 not a primitive characteristic, but results from the fusion of inverted medullary 

 strands with the inner surface of a normal cycle of bundles. Further studies 

 from the same quarter will be awaited with interest— E. C. Jeffrey. 



Potamogeton — While the economic aspect of the growth of various species 

 of Potamogeton in ponds has been the prime object of investigation, Miss 

 Moore3» has presented valuable data upon the habits of growth and reproduc- 



« Sargant, Ethel, and Arber, Agnes, The comparative morphology of the 

 embryo and seedling in the Gramineae. Ann. Botany 29: 161-222. figs. 35. pis. 9, 10. 



38 Worsdell, W. C., The origin and meaning of medullary (intraxylary) phloem 



