346 



SCIENCE. 



[N. S. Vol. III. No. 62. 



rays to pass mucli more readily than others. 

 Flaws in instruments, especially those made 

 of aluminum, might be detected by these 

 rays. Experiment alone will decide whether 

 bacteria will be influenced by the rays in 

 the same manner as certain colonies of or- 

 ganisms are injured by exposure to the direct 

 action of the sun. Park, of New York, has 

 exposed a culture of the diphtheria bacillus 

 for thirty minutes to the rays from a 

 Crookes tube without any result being 

 noted. He who is able to secure a picture 

 of the brain will accomplish more than can 

 be expected from the present state of our 

 knowledge of the X-rays. 



The suggestion has been made that in 

 our large cities skiagraphic institutions 

 should be erected and equipped, to which 

 physicians or surgeons could send patients, 

 and where, under their direction, pictures 

 of the desired portion of the body could be 

 prepared, just as a physician now writes 

 a prescription which is sent to the druggist 

 to be compounded. Our large hospitals 

 where numerous accident cases are brought 

 should have in the near future a plant suf- 

 ficient to prepare skiagraphic reproductions 

 at short notice. 



Henry W. Cattell. 



University of Pennsylvania. 



CURRENT PR0BLE3IS IN PLANT 

 MORPHOLOGY. 



ON SOME CHAEACTEES OF FLOEAL GALLS. 



The growing interest in ecology which is 

 SO marked a feature of botanical investiga- 

 tion during the last five years has occa- 

 sioned new and valuable work on galls, so 

 that now for the first time compendious 

 works have begun to appear, in which a 

 really scientific and adequate account of 

 these curious structures is attainable. An 

 excellent resume in popular style is that 

 given in Kerner and Oliver's Natural His- 

 tory of Plants,Yo\. II., pp. 518-554. Tliat up- 

 ward of 1,600 diiierent kinds of galls have 



been described is noted, and an attempt is 

 made to classify them. With character- 

 istic looseness Kerner divides galls into 

 fungus galls and insect galls, but this is 

 quite inadequate, for algse, among plants, 

 also produce galls, e. g., Phytophysa trcubii 

 W. V. B.,* which attacks the leaves of Pilea 

 at Buitenzorg. And "insects," under which 

 Kerner includes Arachnoidea, are not at 

 all the only gall-producing animals, for' 

 nematodes (afterwards mentioned by Ker- 

 ner) and rotifera are well known as effi- 

 cient causes in cediciogenesis. 



Kerner's classification of galls from a 

 plant anatomical point of view is, however, 

 excellent and is reproduced with some 

 slight modifications in Ludwig's Lehrbuch 

 der Biologie der Pflamen.-\ Fundamentally 

 galls are either simple or compound, as one 

 or several organs take part in their produc- 

 tion. Each class is divided into a number 

 of subclasses, but the details need not be 

 gone into here. The account given by 

 Ludwig is compact and clear. 



The changes produced in flowers and in- 

 florescences when they are subjected to 

 stimulus from a cecidiogenic organism may 

 be classified as: 1. Chlorosis. 2. Multiplica- 

 tion of parts. 3. Metamorphosis of parts. 

 4. Suppression of parts. 5. Hypertrophy, 

 general or restricted. 6. Antholysis. 7. 

 Fusion of parts. 8. Fasciation. Examples 

 of these are as follows : 1. Green flowers of 

 Veronica. 2. Double flowers of Rhododen- 

 dron. 3. Flowers of Valerianella in which 

 petals are substituted for stamens. 4. 

 Flowers of Anemone nemorosa inhibited by 

 PuGcinia fusca. 5. Flowers of Lychnis in 

 which a parasitic Ustilago stimulates the 

 growth of the vestigial stamens of pistillate 

 flowers until they rival in structure the 

 normal stamens of staminate flowers. 6. 

 Flowers of gentians in which the carpels 



* Weber : Zoolog. Erg. Eeis. Niederl. Ost-Ind. 

 Hft. I. 48-71. Leiden, 1890. 

 t Ludwig : 1. c, pp. 98-110. 1895. 



