NA TURE 



46] 



THURSDAY, SEPTEMBER 15, 1892. 



NEW CONTRIBUTIONS TO THE BIOLOGY 



OF PLANTS. 



Beitriige zur Biologie der Pflanzen. Herausge^eben 



von Dr. Ferdinand Cohn. Band 5. Heft 3. 1892. 



TO the new number of Prof. Cohn's publication Dr. 

 Max Scholtz contributes an interesting paper on the 

 nutation of the flower-stalk in poppies and of the ter- 

 minal shoots in Virginian creeper. In both cases the 

 nutation is dependent on the action of gravity, but has 

 nothing to do with the weight of the bud. In the case of 

 poppies the downward curvature of the stalk takes place 

 with sufficient force to lift a weight equal to twice that of 

 the flower-bud. If, however, the flower-bud be removed 

 there is no longer any nutation ; the stalk straightens 

 itself. Vochting had already shown that this is the case 

 even if the amputated bud is tied on again with thread. 

 Dr. Max Scholtz further states that if a weight three times 

 as heavy as the bud is substituted for it, the stalk still 

 straightens itself, and lifts up the weight. The state of 

 the case then is this : the upper part of the flower-stalk, 

 during a certain stage of growth, is in a high degree 

 positively geotropic if it remains in connection with a 

 developing flower-bud, but not otherwise. The author 

 has further succeeded in determining the exact part of 

 the flower-bud which governs the geotropism of the stalk. 

 If the pistil is excised, nutation ceases, the stalk becoming 

 negatively geotropic ; but if all the other whorls of the 

 flower are removed and the pistil left, then nutation goes 

 on as usual. But beyond this, if the ovules are extir- 

 pated, but the wall of the ovary left standing, the nutation 

 is stopped. Hence we arrive at the sinking conclusion 

 that the presence of developing ovules in the young ovary 

 determines the reaction of the flower-stalk towards 

 gravity. A certain analogy is obvious with the irritability 

 of root-tips, investigated by Darwin. Dr. Max Scholtz's 

 observations afford a good example of the extreme com- 

 plexity of those phenomena of growth which a few years 

 ago were thought susceptible of a simple mechanical ex- 

 planation. The author thinks that the nutation is of 

 advantage, inasmuch as the reversed position of the 

 flower-bud allows a better access of light to the developing 

 ovary. As is well known, the flower-stalk ceases to nod 

 when the flower opens ; in other words, as soon as the 

 development of the ovules is completed the flower-stalk 

 becomes as strongly negatively geotropic as it had been 

 positively geotropic before. 



Dr. Max Scholtz has made similar observations on 

 the nodding ends of the main shoots of Ampelopsis 

 qtiinquefolia. Here also the positive geotropism 

 of the younger internodes only exists so long as 

 the terminal bud is present and uninjured. Both 

 here and in the poppies the same part of the stem 

 svhich for a time shows nutation afterwards erects itself, 

 reversing its reaction towards gravity, and also becoming 

 for the first time positively heliotropic. This change in 

 the mode of response to constant external influences is 

 dictated by the embryonic organs at the growing point. 



A paper by Dr. Paul Siedler on the radial sap-current 

 in roots, consists essentially of an anatomical description 

 NO. I 1 94, VOL. 46] 



of the cortex in a number of roots, and does not appear 

 to add much to our previous knowledge. The author 

 believes that in many cases the hypodermal layers act as 

 a water reservoir ; this is not improbable, but no experi- 

 mental evidence is adduced, and the argument from 

 structure alone is scarcely convincing. 



Dr. F. Rosen writes on differences in staining between 

 various parts of the nucleus, and between the sexual 

 nuclei. His work is generally confirmatory of that of 

 the zoologist Auerbach. He finds, on examining the 

 vegetative nuclei of Scilla and Hyacinth that two kinds 

 of nucleoli can be detected in the nucleus ; the one has 

 an affinity for red, the other for' blue stains. The 

 "erythrophilous" bodies are the true nucleoli; the 

 " cyanophilous " granules form part of the chromatin 

 framework. These are simply colour reactions, and are 

 independent of the chemical composition of the stains 

 employed. 



The author's results are much more remarkable in the 

 case of the sexual nuclei. He worked at Liliaceae, and 

 found that the generative nucleus of the pollen-grain 

 takes up blue stains specially, while its vegetative nucleus 

 is conspicuously erythrophilous. In the female organs, on 

 the other hand, not only the nucleus of the ovum, but all 

 the nuclei in the embryo-sac are erythrophilous, while 

 those of the rest of the ovule give blue reactions on double 

 staining. He believes, therefore, that he has detected 

 a qualitative difference between the male and female 

 nuclear substance. His statements apply to the 

 chromatin framework of the respective nuclei. 



These observations are curious, but their significance 

 is very doubtful. The existence of a distinct male and 

 female substance, distinguishable by reagents, is highly 

 improbable in the light of our present knowledge of the 

 phenomena of fertilization. It is noticeable that the 

 author has not investigated the reaction of the sexual 

 nuclei at the time of their fusion. Probably the differ- 

 ences which he has observed, like those recorded by some 

 previous investigators, depend rather on the phase of de- 

 velopment of the nuclei than on their sexual character. 



Prof, G. Hieronymus is the author of two " Contribu- 

 tions to the Morphology and Biology of the Algse." The 

 former of these is on a curious freshwater Alga, Glauco- 

 cystis, hitherto placed among the blue-gteen forms. The 

 author shows that it possesses a perfectly typical nucleus 

 and chromatophores, and must therefore be removed from 

 the Cyanophyceos, and find a place among the higher 

 Algae, probably in the neighbourhood of the Bangiaceas. 

 The same applies to several other genera, which, on 

 account of their colour, have hitherto been classed among 

 the Cyanophyceae, 



The author's second paper is on the organization 

 of the cells of Cyanophyceae (Phycochromacese of Prof. 

 Hieronymus), The existence both of chromatophores 

 and nuclei in these plants has long been a subject of 

 controversy. 



As regards the former question, the author finds that 

 the chlorophyll is contained in distinct granules, ranged 

 in fibrillae, which normally form a single or double layer 

 in the peripheral protoplasm. The blue pigment, how- 

 ever, is dissolved in the cell-sap. He compares the green 

 granules to the "grana" of Arthur Meyer, which, in 

 typical chloroplastids, are the immediate seat of the 



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