99 



mutation, which involves heavy risks, many mutations being 

 lethal, others disadvantageous. But the polyploid species may 

 themselves have arisen by duplication, combined with mutation, 

 and hence it appears that those regions characterized by poly- 

 ploids, while not necessarily the original homes of the genera 

 concerned, have at least been inhabited by them a very long 

 while. Consequently the cytology of all these plants acquires a 

 new interest, and the chromosome count is no longer merely a 

 matter of record, lacking special significance. For instance, 

 with reference to the very recent (Botanical Gazette, April, 

 1926) discussion of Xanthium by Symons, it seems possible 

 that the true X. Wootoni will be found to have fewer chromo- 

 somes than those allied species which occasionally produce 

 fFooloni-Yike. burrs. If so, the genuine X. JVootoni will always 

 breed true, as it did in the experiments of DeVries. 



I notice only one misprint in the eleventh edition: Hippophse 

 for Hippophae. To the American botanist some of the generic 

 arrangements will seem illogical, and indeed the amount of 

 generic division allowed seems to vary with the authority who 

 last revised the group. These catalogues are certainly most 

 useful, and stimulating to botanists in the regions where they 

 are used. It would be a great service to American botany to 

 issue a series of similar lists, dealing with the various major 

 divisions of our country. It is important that the price should 

 be low. The eleventh edition of the London Catalogue, though 

 well printed on good paper, is sold for ten pence (20 cents), and 

 may be had interleaved and bound in limp cloth for a shilling 

 and sixpence. The publisher is Geo. Bell and Sons, 6 Portugal 

 Street, W. C, London. 



T. D. A. COCKERELL 



"TROPICAL WOODS" 



In March, 1925, the School of Forestry of Yale University 

 began the publication, under the name "Tropical Woods," of 

 a small quarterly journal which, under the efficient editorship of 

 Prof. Samuel J. Record, has now reached its seventh number. 

 It is devoted to the forestry and botany of tropical trees, with 

 special reference to those of America. The first five numbers 

 were distributed gratuitously and widely, but with the sixth the 



