Apeil 30, 1897.] 



SCIENCE. 



697 



familiar with its general plan and with the 

 spirit of the author. 



In looking over the bibliography, which in- 

 cludes the more important works consulted by 

 the author and translator, it is interesting to 

 note that the bulletins of the experiment sta- 

 tions in the United States have been given a 

 place, and there are many references in the 

 body of the work to the published investigations 

 of several of these stations. 



In defining the parasitism of the parasitic 

 fungi, on account of the facultative nature of a 

 large number of the species of both parasitic 

 and saprophytic forms, the author believes that 

 it is more correct to consider as parasites those 

 which in their attack respond to the stimuli 

 exerted upon them by living plant cells rather 

 than as an adaptation to nutrition, being in- 

 fluenced in this respect by the researches of 

 Pfeflfer and Miyoshi. According to these in- 

 vestigations the stimulus seems to be a purely 

 chemical one, and Miyoshi has shown that ordi- 

 nary saprophytic fungi, as Penicillium glauewm, 

 may be made to behave like a parasite by in- 

 jecting a two per cent, solution of cane sugar 

 into leaves. 



The terminology applied to those forms which 

 are not strictly obligate parasites or saprophytes 

 is different from that employed by de Bary and 

 others, the present author employing the terms 

 ' hemi-parasites ' and ' hemi-saprophytes. ' The 

 first chapter further deals with the mode of life 

 of the parasitic fungi, their relation to the host 

 and to its diflFerent tissues, and the various modi- 

 fications of the mycelium into absorbent organs 

 for the taking up of nutritive matters. 



In the chapter on the reaction of the host to 

 parasitic attack the work treats of the absorp- 

 tion of cell contents, the absorption of cells and 

 tissues (notably in certain Ustilaginese), the 

 killing of host cells and tissues by ferments, the 

 killing of organs or entire parts, the premature 

 development of buds, preservation of the host 

 plant, arrest of growth, atrophy, hypertrophy, 

 and changes in cell contents of the host. Under 

 the last head among other things is cited a kind 

 of chlorosis produced by certain fungi on the 

 host, when the green parts become bleached 

 and lose their green color, as in the case of the 

 attack of many of the Exoascese. This is 



termed ' mycetogenous chlorosis.' Contrasted 

 with this are those cases which have probably 

 been observed by all students of parasitic fungi, 

 in which the affected portions of the leaves or 

 shoots remain green longer, while the unaf- 

 fected parts become pale and lose their green 

 color. A third case is termed ' mycetogenous 

 chloranthy,' that is the development of green 

 color in the floral parts, as in the petals and 

 stamens of Brassica nigra and Sisymbrium pan- 

 nonicum attacked by Cystopus and Peronospora, 

 and in the flowers of Anemone ranunculoides 

 attacked by ^cidium, punctatum. In some 

 cases of hypertrophy the cell sap assumes 

 a rose color on the sunny side, as in galls, 

 caused by Exobasidium and in the bracts of the 

 catkins of alder attacked by Exoascus. Car- 

 mine and yellow colors also occur, and yellow 

 color may sometimes result from the yellow oil 

 contents of the mycelium lying in the tissues. 

 The accumulation of starch in parts of the host 

 attacked by certain fungi is noted, as in the 

 spruce needles when affected by Lophodermium 

 macrospermum at a time when it is only being 

 slowly formed in unaffected needles. Starch 

 preservation is noted in oak wood destroyed 

 by two fungi simultaneously. This chapter 

 further deals with the effect of the mycelium 

 in dissolving starch grains, wood cell walls and 

 the eflects of fungi on the anatomical structure 

 of their hosts. 



Under ' mutualism ' or ' symbiosis ' in the 

 stricter sense the author first cites the much dis- 

 cussed case of the lichens. Here, the author 

 claims, " as a result of the union of fungus and 

 alga, a living organism originates, which in 

 form necessities, and mode of life is quite new, 

 and differs completely from either of its com- 

 ponents." In dilating upon the evolution of 

 this new organism the author compares it with 

 water, which is the result of the combination of 

 oxygen and hydrogen, or to a certain extent to 

 the new individual, which is produced by the 

 union of sexual cells. ' ' These and other ex- 

 amples, ' ' he says, ' ' will serve to illustrate how 

 we have in the lichen an organism with pe- 

 culiarities of structure and of life widely differ- 

 ing from those of either an alga or a fungus." 

 This unification of two living beings into an indi- 

 vidual whole the author terms 'individuation.' 



