338 BOOKS AND CURRENT LITERATURE 



water Algae, but a good deal is relatively new, and hitherto available 

 only in special papers. 



It is to be hoped that the series of handbooks, of which this is the first, 

 will be carried forward with promptness and vigor. The usefulness of 

 such reviews goes without question. The high price is unfortunate, as 

 the number of readers will be lessened thereby. The book could be 

 more cheaply produced without sacrificing its usefulness. However, 

 the same might be said of Thuret's Etudes Phycologiques, now the 

 delight of the botanical bibliophile. — I. F. Lewis. 



Medullary Rays. — ^The application of comparative anatomy to 

 the criticism of other criteria of relationships is well exemplified in 

 recent studies on the rays of coniferous woods. The sporadic occur- 

 rence of marginal trachoids in the rays of cupressineous woods was 

 earlier observed by several workers, among them Penhallow, who seems 

 to have misinterpreted them. The observation of such cells in a 

 wounded stem of Cunninghamia by Jeffrey^ set the matter in its true 

 light, and this author interpreted the cells as a reversion to the ancestral 

 condition seen for example in Pinus. Miss Gordon^ reported ray 

 tracheids in Sequoia sempervirens, and Miss Holden^ showed that they 

 occasionally occur in various genera of Taxodineae and Cupressineae. 

 As to Abietineae, the earlier Pityoxyla lack marginal cells, while speci- 

 mens from the Upper Cretaceous onward show them.^ They are 

 accordingly of comparatively recent introduction, and while prominent 

 in all pines of the present era, they are apparently in process of dis- 

 appearance in Cedrus,^ and have practically disappeared from Abies, ^ 

 and the Taxodineae and Cupressineae, though they may be recalled 

 by wounding. Mention should be made in this connection of Thomp- 

 son's theory of the origin of these cells.'' — M. A. Chrysler. 



' Jeffrey, E. C. Traumatic Ray Tracheids in Cunninghamia sinensis. Ann. 

 Bot. 22: 593-602, pi. 31. 1908. 



* Gordon, M. Ray Tracheids in Sequoia sem-pervirens. New Phyt. 11: 1-7. 

 1912. 



' Holden, R. Ray Tracheids in the Coniferales. Bot. Gaz. 55: 56-65, pis. 

 1, 2. 1913. 



* Bailey, I. W. A Cretaceous Pityoxylon with Marginal Tracheides. Ann. 

 Bot. 25: 315-325, pi. 26. 1911. 



5 Chrysler, M. A. The Medullary Rays of Cedrus. Bot. Gaz. 59: 387-396. 

 1915. 



6 Thompson, W. P. Ray Tracheids in Abies. Bot. Gaz. 53: 331-338, pis. 24, 

 25. 1912. 



^ Thompson, W. P. The Origin of the Ray Tracheids in the Coniferae. Bot. 

 Gaz. 50: 101-116. 1910. 



