APPENDIX 421 



normal position on the contact-walls assumed in darkness, but is readily overcome by 

 their more powerful phototropism on exposure to diffuse or strong light. 



Frank (Bot. Ztg., 1904, orig., p. 162) finds that the zoospores of Chlamydomonas 

 tingens are attracted by nitrates, phosphates, nitric and carbonic acids, whereas sul- 

 phuric and hydrochloric acids, salts of ammonium and metals, cane-sugar, glycerine, 

 asparagin, and peptone are indifferent. Strong acids and alkali repel, and strong 

 meat-extract (0-3 to 2-0 per cent.) attracts. 



Shibata has investigated the chemotaxis of Isoetes spermatozoids (Jahrb. f. 

 wiss. Bot., Bd. XLI, 1905, p. 561 ; Ber. d. D. Bot. Ges., Bd. xxn, 1905, p. 478). Malic 

 acid and its salts attract in a concentration of 0-00067 P er cent., but free acid repels 

 in one of 0-026 per cent. A few organic acids of similar constitution, such as fumaric 

 acid, act similarly, but more feebly, whereas its stereoisomer, maleic acid, has no 

 attractive action. H, HO, and acid ions repel, as is shown by the dependence of the 

 repellent action on dissociation and concentration. 



Dissociating salts of Ag, and to a less degree of Hg, Cu, Zn, Ni, and Co, 

 exercise a very strong repellent action, but not poisonous alkaloids. Anaesthetics 

 suspend the irritability while locomotion continues. The repulsion is phobic, the 

 attraction tactic. On the chemotaxis of the sperms of Equisetum and of Salvinia see 

 Shibata, Bot. Magazine, Tokyo, Vol. xix, 1905, pp. 39, 51, 79. 



Lidforss (Jahrb. f. wiss. Bot., 1905, Bd. XLI, pp. 65-87) finds that the antherozoids 

 ofMarchantia are positively chemotactic to albumins, globulins, nucleo-albumins, and 

 other proteids, the minimum dilution being 0-0005 per cent., while 5 per cent, solu- 

 tions repel by negative chemotaxis, since the organisms have no osmotactic irrita- 

 bility. They are, however, feebly aerotactic, and are attracted by an extract of the 

 archegoniate heads made in the same way as diastase is extracted from leaves. The 

 proteids mentioned above also attract pollen-tubes (Lidforss, Ber. d. D. bot. Ges., 

 1899, Bd. xvii, p. 236). 



Chemotaxis (infl. of anaesthetics). According to Rothert (Jahrb. f. wiss. Bot., 1904, 

 Bd. xxxix, p. i), chloroform and ether immediately suppress the chemotaxis, aerotaxis, 

 and osmotaxis of Bacterium termo forms, the chemotaxis of Spirillum tenue and Bacillus 

 Solmsii, the aerotaxis of Beggiatoa alba, the chemotaxis of Trepomonas agilis, the 

 chemo- and osmotaxis of Saprolegnia zoospores, and the phototaxis of Euglena 

 viridis, Chlamydomonas, Gonium pectorale, Pandorina morum. In some cases the 

 locomotion is as active as before, in others more or less retarded. 



Weak chloroforming changes the negative phototaxis of Chlamydomonas and 

 Gonium to positive, i.e. renders them less responsive to the higher intensity of light, 

 whereas ether exercises no such effect even in fatal concentrations. 



Elfving, Ueber die Einwirkung von Aether und Chloroform auf die Pflanzen, 

 Ofversigt af Finska Vetenskaps Soc. Forhandlingar xxvm, 1886, found that ether 

 produced this effect, but not chloroform. 



All these reactions are instantaneous, and are independent of the duration of the 

 anaesthetization ; whereas slight doses, which at first affect neither locomotion nor 

 irritability, gradually retard the movement and may exert an ultimately fatal effect 

 before locomotion has ceased. In all cases individual differences are shown, some 

 forms being more sensitive than others. In the case of Gonium, after anaesthetiza- 



