physiologically considered, 485 



albumen : in the former, the embryo lies outside of the albumen, 

 on which account they easily germinate ; whereas, in the latter, 

 the embryo is entirely surrounded by the albumen, for which 

 reason, with the exception of most of the annual or biennial sorts, 

 they are more difficult to vegetate. As they cannot be cut witii 

 advantage, it is usual to sow them late in autumn, with other 

 difficult-growing sorts ; so that when the universal period of 

 germination comes, in the spring, they may be sufficiently pene- 

 trated with moisture. This method is very well suited for sow- 

 ing on a large scale ; but as the seed often perishes during the 

 winter, and the earth becomes sour, or thickly covered with 

 moss, the preferable way for valuable seeds is to sow them in the 

 spring, after they have been soaked for some days previously in 

 warm water. 



In this way very old seeds of Umbelliferse, in which the em- 

 bryo seemed entirely dried up, often germinate quickly, of which 

 I give the following as an example : — In the botanic garden at 

 Bonn, in the spring of 1838, four pans were sown with seed, full 

 ten years old, of jPerula tingitana Z^., and only those in two of 

 the pans were previously soaked. The latter sprung up all 

 together in from ten to twenty daj^s, while of those in the other 

 pans, which were left for trial, only a few plants came up in one 

 pan in the spring of the following year, the rest of the seed 

 having all rotted. 



The process of germination transforms the nourishing matter 

 contained in the seeds, such as starch (amylum) and gluten, into 

 a sugary substance. KirchhoPs experiments show that when 

 starch is stirred with a little cold water, and then boiling water 

 poured on and continually stirred till it forms a consistent mass, 

 such as is used in book-binding; and, after some gluten (gluey 

 matter of plants (Pflanzenleim) and albumen) has been added, 

 the whole placed in a tolerably warm temperature for several 

 days ; the mass by degrees becomes watery and sweet, and part 

 of the starch is changed into gum, and part into sugar. The 

 same effect is produced by boiling the mass with diluted acid, 

 and putting it in a temperature of from 10° to 18° R. {5Q° to 59° 

 Fah.), with or without the influence of the open air. In the latter 

 process, a mass indissoluble in water remains behind, which has 

 been named iignine, starchy woody matter (starkeartigen Holz- 

 stoff ). From these experiments it appears that it is chiefly heat, 

 and the gluten contained in a great many seeds, which cause the 

 transformation of the matter in germination, which we call the 

 process of assimilation. 



There are still many experiments which have been made to 

 accelerate germination open to the consideration of the practical 

 gardener. Alexander von Humboldt was the first to observe 

 that watering with chlorine (Chlorwasser) induced speedy ger- 



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