1881.] Botany. 557 
Nageli, strongest between the nuclei, while growth by apposition 
would only take place at the periphery of the grains. (5) The 
partial grains of compound and half compound grains being more 
watery than simple grains of similar size. 
In the discussion and explanation of these properties, the 
remarkable inner differentiation of starch-grains is first consid- 
ered. The development of simple granules which was found to 
agree in the most important points with the observations of Na- 
geli, excepting the peculiar properties above referred to and belong- 
ing to a limited number of plants, may be summed up as follows: 
(1) Young grains consist of very dense, highly refractive sub- 
stance. (2) Later a less refractive, more watery spot (nucleus) 
According to the generally adopted views of Nageli, these facts 
are held to prove that the inner structure is not due to a succes- 
Sive deposit of alternating more and less dense layers around a 
highly watery primary grain, but that the more watery layers and 
the nucleus have been differentiated within the less watery sub- 
stance, The investigation of the physical properties of starch- 
4 ains leads, however, to an explanation of these properties which 
