APPARATUS OF VEGETABLE PHYSIOLOGY. 251 



special application of the preceding to the investigation of 

 the relation existing between the process of germination 

 and temperature, devised by Prof. Cohn, Director of 

 the Institute of Vegetable Physiology in the University 

 of Breslau. It consists of a chamber with double walls 

 made of tin the space between them being nearly filled 

 with water within which are several tin trays on each of 

 which are several small dishes of porous earthenware. The 

 seeds, after having been soaked for twenty-four hours 

 in water, are placed in the earthenware dishes, water being 

 poured into the tin trays in order to maintain the seeds 

 in a sufficiently moist state. Heat is then applied to the 

 chamber by means of a small regulated gas flame, and the 

 temperature is raised to a degree which previous experi- 

 ments have shown to be the most favourable to the process 

 of germination. 



The use of an apparatus of this kind to the physiologist 

 is obvious. By its assistance he is enabled to control all 

 the conditions upon which the process of germination 

 depends, and he can ensure a supply of material at any 

 time for the investigation of this process either from a 

 physiological or from a morphological point of view. But 

 its usefulness is by no means limited to the study of the 

 process of germination as it occurs in the seeds of the higher 

 plants. It is extremely useful for the purpose of culti- 

 vating various kinds of fungi, since it affords all the 

 conditions necessary for their growth, and by this means, 

 much of the life-history of these fungi may be brought 

 under observation. 



Let us consider for a moment what lessons in Vegetable 

 Physiology this apparatus teaches. To the seeds germin- 

 ating, or to the moulds growing within it, it affords heat, 

 air, and moisture, whilst it shuts out the light from them. 

 Hence we may infer that heat, air, and moisture are 

 essential to the germination of seeds, and to the growth of 

 moulds, whereas the presence of light is unnecessary. 



With this apparatus we can further ascertain what 

 degree of temperature is most favourable to the germin- 

 ation of a seed or to the growth of a fungus, and between 

 what limits of temperature these processes will occur. 

 For instance, it has been found that wheat or barley will 

 germinate at a temperature so low as 5 C., and the highest 



