MICROSCOPICAL RESEARCHES, 
&e. &e. 
INTRODUCTION. 
AxtuovueH plants present so great a variety of external form, 
yet they are no less remarkable for the simplicity of their 
internal structure. This extraordinary diversity in figure is 
produced solely by different modes of junction of simple ele- 
mentary structures, which, though they present various modi- 
fications, are yet throughout essentially the same, namely, cells. 
The entire class of the Cellular plants consists only of cells ; 
many of them are formed solely of homogeneous cells strung 
together, some of even a single cell. In like manner, the Vas- 
cular plants, in their earliest condition, consist merely of simple 
cells; and the pollen-granule, which, according to Schleiden’s 
discovery, is the basis of the new plant, is in its essential parts 
only a cell. In perfectly-developed vascular plants the struc- 
ture is more complex, so that not long since, their elementary 
tissues were distinguished as cellular and fibrous tissue, and 
vessels or spiral-tubes. Researches on the structure, and par- 
ticularly on the development of these tissues, have, however, 
shown that these fibres and spiral-tubes are but elongated cells, 
and the spiral-fibres only spiral-shaped depositions upon the 
internal surface of the cells. Thus the vascular plants consist 
likewise of cells, some of which only have advanced to a higher 
degree of development. The lactiferous vessels are the only 
structure not as yet reduced to cells; but further observations 
are required with respect to their development. According to 
Unger (Aphorismen zur Anatomie und Physiol. der Pflanzen, 
Y 1 
