SOOLOGY AND BOTANY, MICROSCOPY^ ETC. ' 429 



(5) Structure of Organs. 



Orig-in of the lateral roots in Legmninosae and Cncurbitacese*— MM. P. 



van Tiegliem and H. Douliot dissent from the statement of Janczewski, that 

 the secondary roots of Leguminosse and Cucurbitacese are formed in a 

 different way from those of other orders of Dicotyledons. They repeat their 

 previous assertion that the young secondary root derives its nutriment from 

 the cells of the mother-root with which it comes into contact. This may 

 take place in three different ways : — (1) The young lateral root is naked, 

 and its digestion is then direct and complete, as in Ferns, Cycadese, Conifers, 

 Oruciferge, Caryophyllaceae, various Monocotyledones, &c. (2) The young 

 lateral root pushes before it a more or less thick layer of protoplasmic 

 tissue, which continues in a state of activity, and which digests the tissues 

 with which it comes into contact ; this layer of tissue they propose to 

 call the digestive pouch (jpoche). The digestion is here indirect and partial. 

 (3) This pouch soon disappears from the sides of the lateral root, remaining 

 intact only at its apex ; this case is intermediate between the other two. 

 This digestive pouch has been described by previous writers as a false root- 

 cap. The layer of tissue which envelopes and protects the apex of a 

 lateral root is called by the author the cap (coiffe) independently of its 

 origin ; the portion which belongs to the surrounding tissue they now 

 propose to call the pouch, that which belongs to the lateral root itself the 

 calyptra. The lateral roots of Leguminosse and Cucurbitacese have their 

 origin, equally with those of other Dicotyledones, in the pericycle of the 

 primary root or of the stem ; their mode of growth is by means of a strongly 

 developed jDouch. 



Origin of Lateral Organs.f — Herr G. Karsten supports Sachs's statement 

 that the phenomena of growth in plants may all be referred to a common 

 principle, viz. rectangular segmentation. He finds this to be the origin of 

 the secondary roots in all the plants examined, whether monocotyledonous 

 or dicotyledonous. In opposition to Janczewski, he states that the differ- 

 entiation of the meristem takes place only at a comparatively late period. 

 In Lycopodium and Selaginella he finds no apical cell in the young leaf- 

 papillae. As regards Gymnosperms, he agrees with Strasburger rather than 

 Dingier, finding no apical cell either in the rudiments of the leaves or in the 

 growing-point of the stem. In Angiosperms (Elodea, Hippuris, Utricularia) 

 the leaves have the same origin from the growing-point, brought about in all 

 cases by rectangular segmentation of a group of cells, and not by segmenta- 

 tion of a single apical cell, as in mosses and ferns. 



Tubers on the Roots of Leguminosse,^ — Herr F. Benecke confirms the 

 conclusion of Brunchorst,§ that the " bacteroids " found in the tubers on the 

 roots of Leguminosffi are not living bacteria, although endowed with a con- 

 stant swarming motion, but are ordinary protoplasmic structures of the 

 cells, and the tubers receptacles of food-material. His principal argument 

 in support of this view is that, in Vicia Faba, if half of the apex of the root 

 is removed, and the other half gradually developed into a normal root by 

 water-culture, the tubers do not make their appearance until the root has 

 assumed its normal structure, and then in that part which no longer shows 

 9,ny trace of injury. 



* Bull. Soc. Bot. France, viii. (1886) pp. 491-501. Cf. tliis Journal, ante, p. 262. 



t Karsten, G., 'Ueb. d. Anlage seitlicher Organe,' 32 pp., 3 pis., and 78 figs., 

 Leipzig, 1886. 



* But. Centralbl., xxix. (1887) pp. 53-4. § See this Journal, 1886, p. 271. 



