904 



SCIENCE 



[N. S. Vol. XXIX. No. 753 



mental data showing that the inhibiting factors 

 of bog conditions are in part due to the presence 

 of injurious toxic water-soluble substances, reac- 

 tions of the plants themselves, that such toxicity 

 can be corrected by various methods, and that the 

 plants grown in solutions thus treated show not 

 only accelerated growth and an increase in trans- 

 piration, but also an increase in the green and 

 dry weights of the plants. 



Further experiments were undertaken to deter- 

 mine whether the toxins of bog water which are 

 harmful to agricultural plants in water cultures 

 are injurious also to plants growing in soil. A 

 series of soils, ranging from pure quartz, sand and 

 clay to humus were infected by shaking each with 

 bog water, and filtering off the solutions. The 

 results of these experiments indicate: (1) that 

 the bog solutions thus treated become highly bene- 

 ficial, (2) that soils absorb the toxins present in 

 bog water, (3) that the soils are infected when 

 treated in this manner and cease to yield a normal 

 growth of plants when compared with similar soils 

 serving as controls. 



Initiating Lioheno-ecologic Studies in the Ken- 

 tucky Mountains : Bkuce Pink, Miami Univer- 

 sity, Oxford, O. 



The writer has long felt that most of the prob- 

 lems of lichen ecology require an unusually long 

 time for their solution and during the past few 

 months has been able to initiate such studies in 

 two places with a view to continuing the work 

 begun through many years. The work in the 

 Kentucky mountains was done on the forest re- 

 serve of Berea College, five miles from Berea, Ky. 

 This locality in the foot-hills of the Cumberland 

 Mountains was selected because the area is to 

 remain undisturbed. Thirty-one areas of varying 

 size and form were marked off, some of them left 

 undisturbed after taking careful notes of the size 

 and condition of development of the lichens within 

 them, others denuded to a considerable depth be- 

 low the surface of the soil or rock, while on others 

 the plants were only partially destroyed, the ob- 

 ject being to watch the rate of growth, invasion, 

 regeneration, etc. The areas were numbered and 

 dated, and were selected in groups so that the 

 study of ecologic factors to follow with instru- 

 ments may be facilitated as much as possible. 

 Descriptions of Species of Opuntia: David Grif- 

 fiths, U. S. Department of Agriculture, Wash- 

 ington, D. C. 



An effort was made in the paper to show the 

 relative value of diagnostic characters in this 

 group of plants, and to show how different con- 



ditions radically affect these characters. A scale 

 of points is made out to show a proposed sequence 

 in descriptive literature. Stress was placed upon 

 the necessity of field studies and descriptions 

 drawn therein which shall describe the entire 

 plant instead of a terminal joint or two, as has 

 usually been done. 

 Physiological Studies on the HymenophyllaoecB : 



FoEEEST Sheeve, Carnegie Desert Laboratory, 



Tucson, Ariz. 



Both physiological and anatomical evidence has 

 been obtained to show that the leaves are the 

 principal water-absorbing surfaces, and that there 

 is very limited conduction of water in the vessels. 

 Most Hymenophyllacese are capable of withstand- 

 ing total submergence in well-aerated water for 

 one month. Fragments of leaves with as few as 

 ten cells are capable of maintaining normal ap- 

 pearance in dilute nutrient solutions for over one 

 month. Most Hymenophyllacese are incapable of 

 enduring a continued humidity as low as 60 per 

 cent. Several hairy forms are able to endure low 

 humidities of brief duration, and even occasional 

 insolation. These forms are capable of surviving 

 without liquid water if kept in air of over 90 per 

 cent, humidity, and will continue to grow under 

 these conditions. Isolated leaves show an ability 

 to gain steadily in weight when kept in moist air, 

 whereas controls killed in various reagents lost 

 weights as did also the leaves of other species 

 without hairs. 

 The Life History of Griffithsia Bornetiana: I. F. 



Lewis, Randolph-Macon College, Ashland, Va. 



The vegetative structures, tetraspores, anther- 

 idia, procarps and cystocarps were described in de- 

 tail, as well as the germination of the spores and 

 the development of the sporelings. Antheridia, 

 cystocarps and tetraspores occur on separate in- 

 dividuals which are almost identical in vegetative 

 structure. The size, shape and arrangement of 

 the cells are the same in the different forms, as 

 are also the size of the nuclei and the number of 

 nuclei in each cell. In mitosis, however, the 

 nuclei of the sexual plants show seven chromo- 

 somes, and the nuclei of the tetrasporic plants 

 about twice that number. The reduction of the 

 number of chromosomes takes place in the two 

 divisions in the tetraspore mother cell. The double 

 number is restored by the union of the gametes. 

 The conclusion is drawn that the carpospores, on 

 germination, give rise to tetrasporic plants and 

 the tetraspores to sexual plants. In the alterna- 

 tion of generations thus arising, the sexual plants 

 are to be considered as forming the " x-genera- 



