ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 451 



Dicotyledons, there is not in nature any sharp dividing line hetween 

 the different kinds of underground stem described as bulb, tuber, root- 

 stock (rhizome), &c. They pass into one another through a number of 

 intermediate forms which it is difficult to classify. 



Aerial Stems.* — M. L. Flot makes the following observations on the 

 aerial stems of certain plants : — (Ajuga reptans, Linaria spuria, Vinca 

 minor). The endoderm is more developed in horizontal stems. The 

 fibrovascular bundles either early form a continuous arc, or their indi- 

 viduality disappears almost completely. The thickness of this arc is 

 always more considerable than the corresponding part in vertical stems. 

 The pith is less developed in horizontal stems. These facts entirely 

 accord with those that have been described by M. Costantin.f The 

 author, in conclusion, asks if it is not remarkable that absolutely com- 

 parable stems, living in the same surroundings, should have a different 

 structure following the influence of geotropism ? 



Anatomy of Annual Branches and Inflorescences. $ — According to 

 Herr J. Trautwein, there are no less than four distinct currents in a 

 plant at the time of the unfolding of the leaves and flowers. The first 

 carries up through the xylem the water and all inorganic substances 

 dissolved in it. The second, the soft bast, is the medium for the trans- 

 port of the nitrogenous substances or albuminoids. The third current, 

 which conducts carbohydrates and oils, takes place chiefly through the 

 cortical parenchyma. The author discusses in detail the relative de- 

 velopment of the tissues through which these currents pass in the 

 various portions of an annual stem. The general result of his observa- 

 tions is that all variations in the anatomical structure of the axial parts 

 of plants are dependent solely on their usefulness and adaptability for 

 the advantage of the organ in question. It is in this way that the flower 

 acts on the axis which supports it. 



Structure of the Leaves of certain of the Coniferge.§ — M. A. Daguil- 

 lon calls attention to the well-known fact that in many of the Coniferae 

 the leaves inserted on the principal stem are different in appearance and 

 in form from those borne by the lateral branches. The author has 

 endeavoured to ascertain whether this external dimorphism corre- 

 sponds to any difference of structure. In Picea excelsa the chief 

 difference between the stem-leaves and the branch-leaves is that the 

 latter are very much more flattened. The endoderm in the stem-leaves 

 of this tree is composed of twenty-two cells, while in branch-leaves 

 there are only sixteen. The liber and conjunctive parenchyma of the 

 vein of the leaf are also represented by fewer elements in the branch- 

 leaves. 



Comparative Morphology of the Flower. || — From the examination of 

 flowers belonging to a large number of natural orders, Herr K. Schumann 

 defends the older view that all the whorls of plants are foliar organs ; all 

 the known facts being reconcileable with this theory, which is also 

 simpler than any other that has been proposed. He also adheres to the 



* Bull. Soc. Bot. France, xxxv. (1888) pp. 54-6. 

 t Cf. this Journal, 1884, p. 252. 



X Trautwein, J., ' Ueb. Anatomie einj'ahriger Zweige u. Bliitenstandachsen ' 

 40 pp., Halle, 1885. See Bot. Centralbl., xxxiii. (1888) p. 201. 

 § Bull. Soc. Bot. France, xxxv. (1888) pp. 57-61. 

 j| Pringsheim's Jahrb. f. Wiss. Bot., xviii. (1887) pp. 133-93 (2 pis.). 



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