286 



SCIENCE 



[N. S. Vol. XLIII. No. 1104 



The following papers were given by invitation 

 of the council, and will appear in the American 

 Journal of Botany: 



"The Specificity of Proteins and Starches in 

 relation to Genera, Species and Varieties," by 

 Professor Edw. T. Eeichert. 



"The Mechanics of Dormancy in Plants," by 

 Professor William Crocker. 



' ' The Periodicity of Freshwater Algae, ' ' by 

 Professor E. N. Transeau. 



Joint sessions were held with Section G, Ameri- 

 can Association for the Advancement of Science 

 and with the American Phytopathological Society, 

 in addition to three general sessions of the society 

 and two sessions of the Physiological Section. The 

 titles and abstracts of the 69 papers follow: 



The Bearing of Certain Senile Changes in Plants 

 on Present Theories of Senility: H. M. Bene- 

 dict. 



Present theories of senility are based almost 

 exclusively upon the study of senile degeneration 

 in animal cells and organs. 



Now that typical senile degenerations in Vitis 

 vulpina and other perennial plants have been 

 shown to occur, senility seems to be more inher- 

 ently connected with living matter than was for- 

 merly supposed to be the ease. Theories of senility, 

 if true, must therefore be as applicable to senile 

 degeneration in plants as in animals. The nine 

 more common theories of senility are stated and ■ 

 classified, and examined in the light of the new 

 data obtained from plants. Of these the theory, 

 first advanced by Kassowitz (1899) and sup- 

 ported by Hertwig and Childs, that senility is due 

 to an accumulation of inert catabolic products, is 

 open to the least objection. A suggestion is 

 offered that a more fundamental cause of senility 

 than this may be found in the colloidal constitu- 

 tion of protoplasm with its units in the form of 

 molecular complexes. The tendency, exhibited by 

 certain non-living colloids, of a progressive change 

 toward closer approximation of the molecules con- 

 stituting the unit, for example, if also occurring 

 in protoplasm would bring about changes in water 

 content, permeability and in other characters which 

 in turn might produce the accumulation of inert 

 or toxic catabolic products. 



The Mutual JSelations of Host and Parasite in the 



Genus Gymnosporangium : B. 0. Dodge. 



It has been previously shown that the leaf form 



of Gymnosporangium on Cham-cecyparis will infect 



Aronia and Amelancliier, giving two different 



types of fficidia. The galls produced on these 

 hosts are also characteristically different. Later 

 experiments show that different species of Ame- 

 lanchier when infected with the stem form, Gym- 

 nosporangium biseptatum, develop different types 

 of galls. Variation in the dimensions of the 

 fficidia are also quite marked. This is in line with 

 the results obtained by Long in connection with 

 his experiments with Pucoinia ellisiana and P. 

 andropogonis, and Pammel's observations on the 

 variation in the form of the peridial cells, etc., of 

 Gymnosporangium macropus found on different 

 hosts. 



What are Chondriosomes ? D. M. Mottieb. 



Argument. — If meristematic tissues of various 

 plants are fixed in a certain mixture of chro- 

 mosmie acid and sections made therefrom are 

 stained with iron-hematoxylin or crystal violet 

 (Benda's formula), there will be revealed in the 

 majority of cells, in addition to the well-known 

 and familiar cell contents, many small granules, 

 chains of granules or rods of uniform structure 

 but of variable size, that stain blue with crystal 

 violet or black with the iron-hematoxylin. These 

 have been described by various observers as chon- 

 driosomes. In the roots of higher plants many of 

 these chondriosomes become leucoplasts, while in 

 the stem they may develop into chloroplasts. 

 Chondriosomes of this nature have been reported 

 from a wide range of families among both higher 

 and lower plants by Guilliermond and others. 

 Different functions have been attributed to these 

 bodies in different plants and in different parts 

 of the same plant. The writer is in harmony with 

 the view that certain so-called chondriosomes be- 

 come leucoplasts in the root and chloroplasts in the 

 stem. It is argued that in the cells of certain 

 plants examined there are present in addition to 

 these plastids other bodies similar in structure 

 and in reaction to fixing fluids and stains, to the 

 above-mentioned plastids, which do not develop into 

 either leucoplasts or chloroplasts. These bodies 

 are always present in some form (granules or deli- 

 cate rods) in all cells, reaching a greater develop- 

 ment in some cells than in others. They are 

 permanent organs which should be given morpho- 

 logical rank with the nucleus and with the pri- 

 mordia of chloroplasts and leucoplasts. No homol- 

 ogy is claimed between the bodies here under con- 

 sideration and the chondriosomes of animal cells. 

 It is suggested that in function these bodies may 

 be concerned in various ways with the metabol- 

 ism of the cell, and that, if the cytoplasm is con- 



