MKTALS OF THE ALKALINK EAIlTHS. 45 



— since the puMimtiijii (jf \u\. i. — -for the application of the dii»- 

 sooiutioii thi'Oi-v to the stiuly of the action of |KjisonK on micro- 

 organisms (^sj 79 un<l 8j), and for tlie useful conchisions that may 

 be ihawii tlicrffroui with rt'j.Mril to jUiirtical ilisinfertion. 



In connection witii ma^jncsium, indirect rcferencr lias aUx-aJy 

 been made to calcium, inasmuch as Naegeli's assumption that 

 this metal could replace magnesium was sUited to liave been 

 refute<l. There still remains, however, tin' less impoitiint <pies- 

 tion whetiiei- calcium is iit all essential to the structure of 

 fungi. On this point Winogradsky, in a previously citetl 

 resoiiivh. found Mijfudtrnni rini still capable of thriving in 

 a nutrient medium free from calcium (and also from barium 

 and strontium). The same results were obt{iine<l by II. Muliscii 

 (II.) and \V. liEXECKK (II.) in their exjieriments with Aifju'n/illuji 

 niyer : so we may well assume that calcium is not e.s.sential 

 to the growth of fungi. Vntil a short time ago it was consideretl 

 that this peculiarity afforded a thorough me^ms of distinction 

 between the fungi and green plants. However, it has recently 

 been foun»l by II. MoLiscii (iV.) that certiiin (but not all!) of 

 the al;ia> will thrive in the absence of CJilcium. c.7. Stichoroccuji 

 bat-dlaris Na*geli, Uldhi'ix snbtilis Kuetzing, but not Vaucheria 

 or Spiro'iijra. For the future, therefore, the axiom must be 

 changed, and calcium regarded as indispen.sjible for the higher 

 green plants, but not essential to the fungi and to certtiin 

 algie. 



80 far as Ivirium and strontium are concerned, it has been 

 placetl lieyond doubt that tho.se two metals are not only u.seless, 

 but also injurious, and act as poi.sons toward the fungi. Thus, 

 for example, in the experimentHS of E. tiuenther, the develo|>- 

 ment of sowings of liliiiujiUK HKjririuin cea.sed in presence of 

 1.0 per cent, of barium nitnite, or 1.5 per cent, of strontium 

 nitnite, in the nutrient .solution. Even calcium, it may bo 

 remarked in passing, is capable of acting injuriously when 

 present in larger tpi;intities, the last-named worker having 

 found the limit of safety to be 4 per cent, of cjilcium nitrate in 

 the case of the sivme J'Jn/coniifces. 



i 230.- Elements of the Iron Group. 



On the fact that iron had liei'u shown uiiii>pen.-<i mc i" lae 

 formation of chloroph\ 11, and therefore essential to the a.ssimi- 

 lative power of green plants, was ba,sed the opinion, long 

 inianimously current among mycologists— f.7. Adolk Mayek(I.) 

 in connection with yea.st, and 0. Na'geli — that the fungi, being 

 destitute of chlorophyll, do not retjuire iron. This a.ssumpliou 

 was lirst put to the test by J. Kaii.ix (l.i in 1S70, the results 

 slunvinii that, in presence of iron, cultures of Asit r<fillu.< nu/tr 

 throve more vigorously in solutions of nutrient sjilt^ conUiining 



