AMERICAN 
JOURNAL OF BOTANY 
Vol. VI June, 1919 No. 6 
A STUDY OF PLASTIDS AND MITOCHONDRIA IN PRESSIA 
AND CORN 
W. C. Twiss 
In this paper certain observations upon plastids and mitochondria are 
recorded. In my opinion it would be premature as yet to formulate any 
conclusions as to the fundamental significance of these bodies, though the 
preparations I have obtained are clean-cut and definite. 
In order to make clear the position assumed in regard to the structures 
in question, it may be well to state, at the outset, that the term plastid will 
be used to include not only the leuco-, chloro-, and chromoplasts, but also 
the Anlagen for the same. The name mitochondria, on the other hand, 
will be restricted to those granules which are not, in general, preserved by 
the usual methods of fixation — those which, in other words, are dissolved 
in acetic acid or in alcohol and are fixed by the use of osmic acid, formalin, 
etc. The mitochondria, moreover, color more or less specifically with 
various stains. I -shall in general use Benda's term mitochondria, rather 
than others that have been proposed, though the etymology of the word 
implies a thread-like form not always present. 
In cells prepared by what are known as the mitochondrial methods, 
these bodies, by reason of their number and intense affinity for the dyes 
become in many cases quite the most striking features of the protoplast. 
The only reason that they were neglected by cytologists for so long a time is 
the fact that they are dissolved by the processes commonly used to demon- 
strate nuclear phenomena. 
Interest in the granular constituents of the cytoplasm has greatly in- 
creased in the last few years, though the idea of their importance is not a 
new one. To Altmann, in 1886, is due the formulation of what is generally 
known as the grajiular theory of protoplasmic structure. Hanstein, in 
1882, had maintained that protoplasm is made up of minute granules, which 
he termed microsomes, and a homogeneous fluid in which the microsomes 
float. Altmann, using a special technique, consisting essentially of fixation 
with osmic acid and potassium dichromate, was able to demonstrate the 
presence in various tissue cells, as well as in the chromosomes, of numerous 
granules to which he gave the name of biohlasts. These bodies he regarded 
as possessing an independent existence, and to them he imputed the'power 
of growth and of multiplication by division. He also believed that they 
[The Journal for May (6: 181-216) was issued June 20, 1919.] 
217 
