H7 



cells on the plate and watch their germination under the microscope. The blue 

 colour is then commonly seen to disappear before the formation of buds begins. 

 But many of the later germinating cells remain blue and produce colourless daugther- 

 cells. I never saw young cells taking the least trace of blue from the mother-cell. 



But if the dried cells are beforehand allowed to swell up in wort or in water and 

 if the soaked material is laid in the methyleneblue solution, which is the usual way 

 to effect the colour reaction, the result is quite different. Then only part of the cells 

 assume the colour and this part is the smaller as the cells have longer remained in the 

 uncoloured solution. A certain percentage, however, continue to take up the colour 

 without having lost their reproductive power, and it seems to be very difficult to 

 soak these cells with water. 



The simplest way to effect these experiments is by using dry yeast, quite free, 

 or nearly so from dead cells. I obtained it by centrifugation of the small-celled 

 variety of pressed yeast from strong fermentations, these being in their most 



active state. 



To this end it was cultivated at 28 C. in nearly neutral wort, after 6 to 8 

 hours brought into the centrifuge, and then quickly transferred to filterpaper in a 

 thin layer for desiccation. 



The large-celled variety of pressed yeast is less resistant to drying. To com- 

 pare the two varieties, of which the smallcelled is richer in protoplasm than the 

 other, the yeast must very cautiously be dried, first at low temperature, e.g. 25 C., 

 then at a higher one, e.g. 50 C. This precaution is not, however, necessary to render 

 the blue-colouring of the dry living cells visible; to this end drying of common 

 yeast at room temperature will do. 



I have, however, also met with commercial dry yeast satisfying the requirement 

 of containing hardly any dead cells at all, namely the Konservierte Getreide 

 Brennerei Hefe of the yeast works of H e 1 b i n g in Hamburg, which was sent 

 directly from the manufactory. This preparation is delivered in solidly closed tins, 

 but after some time it loses its power of growth and^fermentation; its quality thus 

 evidently depends on the length of time past since its fabrication. It seems that this 

 loss corresponds to that of the germinative power of seeds, which depends on their 

 state of humidity. I posses some more preparations from the same factory, that 

 have hardly any fermentative power and contain no cells fit for reproduction, but 

 they have not been directly got from the manufactory and are already some 

 years old. 



When using seed of Brassica rapa, saked in solutions of i per 1000 or less of 

 methyleneblue, the pigment penetrates through the seed coat into the germ, which 

 partly colours blue. The germroot takes up the earliest; then follows a triangular 

 field on the outer of the two seedlobes, which lie folded up in the seed. The base 

 of the triangle, which colours first and most intensely, lies at that margin of the 

 cotyledo, which is turned towards the germroot. 



Obviously the pigment has very quickly penetrated through the micropyle of 

 the seed, and only later through the seed coat. With stronger methyleneblue solutions 

 the experiments do not succeed much better, because then the pigment accumulates 

 so much in the seed coat, that even water can only enter with difficulty. After 24 

 hours such seeds are but imperfectly swollen but, somewhat later, the germination 



