132 TEXT-BOOK OF FUNGI 



has no columella, and the sporangial wall. is persistent. 

 Bachmann has shown that in this species the various com- 

 binations of -the two forms of sporangia, or the absence of 

 either, depend entirely on external conditions. Such 

 conditions turn on the chemical composition of food, its 

 degree of concentration, relative degree of humidity, tem- 

 perature, etc. Any given combination of the two forms of 

 sporangia is constant, so long as the composition of the 

 food and external conditions are also constant. 



Varied conditions also affect the external characteristics 

 of spores, and under some instances a totally different form 

 of spore is produced. Biffen says that chlamydospores of 

 Acrospeira mirabilis, when grown in air, have a thick, 

 brown, warted wall ; when grown in water, the wall is thin, 

 smooth, and uncarbonised. 



Klebs's researches throw a new light on laboratory 

 cultures; many of the discrepancies as to results, when 

 dealing with the same kind of fungus, could probably be 

 explained on the ground of differences, chemical and 

 physical, experienced by the different organisms under 

 observation. It is also possible that the general principle 

 enunciated may account for the well-known herding 

 together, in different localities, of male or female plants 

 respectively, in the case of monoecious species. 



Bachmann, Bot. Ztg., 1895, P- I0 7- 



Biffen, Proc. Cambr. Phil. Soc., n, p. 136 (1901). 



Klebs, Pringsh. Jahrb., 33, p. 513 (1889). 



Ray a long and interesting account of variation in the 



lower fungi, due to environment, Rev. Gen. Bot., 9 (1897). 



Raciborski respecting influence of food and sur- 



