ZOOLOGY AND BOTANY,. MICROSCOPY, ETC. 615 



Movements of Irritation of Multicellular Organs.* — Herr J. Wort- 

 mann confirms by fresh observations bis previous conclusion tbat the 

 curvatures of irritation of invested cells, or of masses of cells, which 

 take place during growth, depend on movements of the proto- 

 plasm. In the organ observed, the root of PJiaseolus multiflcyrus, he 

 finds, whenever there is geotropic irritation, a more or less abundant 

 transference both of starch and of protoplasm to the parts where a strong 

 formation of cellulose takes place. This fact furnishes a strong 

 argument in favour of De Vries's view f that the transport of formative 

 materials in the plant does not take place by osmosis, but is effected 

 through the movements of the protoplasm-body. 



Irritability of Growing Parts of Plants.^ — Prof. E. Godlewski 

 supports the views of Wortmann § with regard to the nature of this 

 phenomenon. He classifies the various phenomena belonging to this 

 category under the following heads, viz. : — 



(1) Phenomena which must be regarded as resulting from the 

 positive geotropism of the specific protoplasm of the root. Under this 

 head come the geotropic downward curvatures of roots removed from their 

 normal position, and the facts that when shoots are hung horizontally in 

 moist air, adventitious roots are formed only on the under side ; that 

 when a cut shoot is hung vertically in natural position, adventitious 

 roots are formed only at the basiscopic end ; that in general roots form 

 more readily in the basiscopic than in the acroscopic portion of a shoot ; 

 and that in the bulbils of Marchantieae the rhizoids grow only on the 

 under surface. 



(2) Phenomena which result from the negative heliotropism of the 

 specific protoplasm of the root : — The negatively heliotropic curvature of 

 many roots and root-hairs when more strongly illuminated on one side ; 

 the retarding effect of light on the new formation and development of 

 the rudiments of roots ; the formation of adventitious roots exclusively 

 on one side of an organ illuminated on one side only, such as ivy-shoots, 

 prothallia of ferns, &c. 



(3) Phenomena resulting from the positive hydrotropism of the 

 specific protoplasm of the root : — The curvature of roots in the direction 

 of the greater moisture ; the favourable influence of moisture on the 

 fresh formation and development of the rudiments of roots ; the fact that 

 the roots of plants growing on a block of turf rotating on a clinostat 

 become closely attached to, or even grow into the turf. 



(4) Phenomena resulting from the negative geotropism of the 

 specific protoplasm of the shoot : — The geotropic curving upwards of 

 growing shoots removed from their normal position ; and the 

 facts that on a horizontal shoot, whether cut or still attached to the 

 parent plant and placed in moist air, the buds which face upwards grow 

 much more rapidly than those tliat face downwards, the latter often 

 remaining quite dormant ; that, when a plant is reversed, new shoots are 

 formed on its oldest part, where they would not be formed if the plant 

 were in its natural position ; and that when cut pieces of a shoot or root 

 are placed in moist air, regeneration of the buds takes place at the 

 acroscopic end of the shoot, and at the basiscopic end of the root. 



* Ber. Deutsch. Bot. GeseU., v. (1887) pp. 458-68 (2 figs.). Cf. this Journal 

 ante, p. 259. t See this Journal, 1885, p. 665. 



% Bot. Centralbl., xxxiv. (1888) pp. 82-5, 143-6, 181-4, 211-3. 

 § See this Journal, ante, p. 259. 



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