BOTANY. 



93 



1880 by Tangl and Frommann ; in 1882 and 

 1883 Eussow and W. Gardiner gave additional 

 facts ; and it now amounts to a demonstration. 



It is believed that this connection exists in 

 many parts of the plant, as it has been found 

 to exist between the cells of the bast, cells in 

 young embryos, in young fibro- vascular bun- 

 dles, and in cells at the base of the leaves of 

 many leguminous plants, particularly those 

 plants with either sensitive or nyctitropous 

 leaves. As such pitted cells occur in great 

 abundance at this point, it is thought that the 

 sudden movement of the leaves of the sensi- 

 tive-plants, when disturbed, may be due to the 

 readiness with which the sudden shock is com- 

 municated through the connecting protoplas- 

 mic filaments to every cell at the base of the 

 leaf-stalk, thereby causing a sufficient contrac- 

 tion in all the cells and the contained proto- 

 plasm, to draw the leaf downward. 



In the domain of physiology proper, Prings- 

 heim's experiments on the office of the 

 chlorophyll-pigment in its relation to the pro- 

 cesses of assimilation, created considerable 

 interest from 1878 to 1881. He had a micro- 

 scope and other appliances constructed pur- 

 posely for the experiments, and came to the 

 conclusion that the chlorophyll-pigment acted 

 merely as a screen to protect from too strong 

 light the protoplasm of the chlorophyll-body, 

 which in reality performed the act of assimila- 

 tion. This discovery was generally accepted 

 until in 1883 T. W. Engelraann claimed that 

 assimilation would not take place in any cell 

 or protoplasm where the chlorophyll was ab- 

 sent, no matter how favorably modified the 

 light might be. It is therefore still one of the 

 unsolved problems. 



The production of starch-grains from chloro- 

 phyll-bodies has been known for some time, 

 but Schimper made the important discovery in 



1881 that all starch-grains, so far as examined, 

 in parts not exposed to the light, as tubers, 

 etc., arose from granules similar in form to 

 chlorophyll-bodies, but destitute of chlorophyll- 

 green, so that, instead of arising spontaneously 

 in the cell, they arise always from either green 

 or colorless corpuscles of protoplasm. 



This period will always be remarkable for 

 the appearance of a conspicuous group of 

 Charles Darwin's works, and "Darwiniana," 

 by other authors. Between 1875 and 1881 he 

 published " Insectivorous Plants " ; the re- 

 vised edition of " Movements of Climbing 

 Plants " ; "The Effects of Cross- and Self-Fer- 

 tilization"; "Different Forms of Flowers on 

 Plants of the Same Species"; and "The 

 Power of Movement in Plants." It is need- 

 less to say that in the field indicated by the 

 above titles, and in general acuteness of ob- 

 servation and generalization, he was without 

 a rival. The rapid appearance of these works 

 occasioned discussion and stimulated work 

 everywhere. In 1873 Hermann Muller's "Fer- 

 tilization of Flowers by Insects" appeared in 

 German, and in 1883 in English. It is a rich 



store-house of observations in this peculiar 

 field, and invaluable to the student of these 

 phenomena. In the death of Darwin in 1882, 

 and of Mtiller in 1883, ends a period of this 

 peculiar literature which Darwin opened in 

 1862 by the publication of " Various Contriv- 

 ances by which Orchids are Fertilized by In- 

 sects." In no other part of plant-physiology 

 has America contributed any original work 

 recently, but Prof. Trelease has published a 

 series of excellent studies on fertilization by 

 the aid of insects, which deserve mention. 



Thallophytes : (1) Bacteria. No department of 

 botanical literature has received greater acces- 

 sions in ten years than that relating to bacte- 

 ria. Though these are written largely from 

 the stand-point of pathology, nearly all the 

 valuable papers are of interest to botanists. 

 The first volume of Cohn's "Beitrage" was 

 published in 1872; the second and third in 

 1876-'79. Interest in these organisms has in- 

 creased from 1872 to the present time, and 

 papers by eminent plant-physiologists have 

 appeared in rapid succession. Robert Koch, 

 Nageli, Buchner, Ktihn, and many others, 

 have published results of experiments, some of 

 them showing wonderful patience, care, and 

 skill. The recent work of Koch has attracted 

 the attention of the world; for he claims to 

 have demonstrated that malignant authrax, 

 tuberculosis, and cholera are each caused by a 

 different species of Bacillus (see TUBEECLE 

 BACILLUS, in "Annual Cyclopaedia" for 1883). 

 That of cholera is comma-shaped, those of an- \ 

 thrax and consumption rod-like, but perfectly 

 distinct from each other, and from other forms. 

 He has explained his laborious, careful meth- 

 ods of experiment, and his mode of getting 

 pure cultures, so as to inoculate healthy sub- 

 jects with undoubted specimens of the particu- 

 lar Bacillus. It is sufficient to say that he has 

 convinced many medical and botanical experts 

 of the soundness of his conclusions. But he 

 has also met with violent criticism, although 

 nearly all the experiments, opposed or nega- 

 tive in their results, performed by his critics, 

 are far below his own in thoroughness and 

 completeness. He denies that tuberculosis is 

 hereditary, but says it should be classed as a 

 contagious disease; and that, knowing the 

 BaciUus producing this disease and cholera, 

 and the conditions promoting their develop- 

 ment, it will be possible to adopt effective 

 means to prevent the spread of such diseases. 



Although it is asserted frequently that the 

 organisms accompanying various other malig- 

 nant diseases are the cause of such diseases, 

 there is no proof in favor of this assertion any- 

 where nearly as adequate as that afforded by 

 Koch in respect to the three mentioned. The 

 botanical aspect of these investigations is 

 chiefly confined to the question, Are these 

 forms of bacteria, asserted to be peculiar to 

 certain diseases, or pathogenic conditions, 

 really distinct species of organisms, or are 

 they only modifications of a few forms, occa- 



