52 VAN TII^HEM AND LE MONNIER. 



position noted. No doubt, also, we must trust to chance for 

 success in only introducing a single spore into a drop, but in 

 a large series of experiments chance is sure sometimes to 

 favour us, and if we are careful to sow the smallest possible 

 number, it is generally possible to fix one's attention on a 

 particular spore and keep that steadily under observation. 



The minute quantity of nutritive fluid which suffices for 

 successful culture is really astonishing, but the result of our 

 observations leaves no doubt on that head. The liquids 

 ■which we have most frequently employed are orange-juice 

 boiled and filtered which is an acid and saccharine liquid, and 

 decoction of horse-dung also boiled and filtered which is 

 a neutral and alkaline one rich in nitrogenous principles. 

 The latter is suitable for the culture of a much larger num- 

 ber of species than the first, but it is apparently poorer in 

 nutritive matters, since the mycelium is always much less 

 vigorous in it. It has also the additional disadvantage of 

 lending itself very readily to the development of bacteria, 

 which are destructive to the cultures. Orange-juice, being 

 acid, is not open to this objection, and the only enemy to fear 

 Avith it is PenicilUum glaucum ; we have given it the prefer- 

 ence whenever possible. In addition, we have also em- 

 ployed, for the sake of comparison, brewers' wort, ordinary 

 water, and a saline solution of the following composition, 

 with or without the addition of 7 grms. of sugar : — 



It must be remarked that the causes of failure in these 

 cell-cultures are very different, and by no means obvious. 

 The condition of the spores, especially as to age, exerts an 

 effect which must not be attributed to the nutrient medium. 

 Too much importance must not, therefore, be attached to 

 particular features ; at the best they will only have a negative 

 value. 



General character of the group of Mucorini. 



The characters which define a group of fungi should be 

 drawn from the vegetative system or mycelium ; the single 

 sexual reproductive apparatus ; the often extremely poly- 

 morphic asexual reproductive structures, and the order in 

 which these different arrangements succeed one another, 

 and which consequently determines the alternation of 

 generations. 



