PLANTS KNOWN BY THEIR POLLEN-GRAINS, ETC. 261 
British Botany.” For example, of the section with yellow flowers 
and divided leaves of the order Eanunculacese, we shall find the 
pollen-grains nearly or quite round and smooth, commonly 
with the usual scars, and about g diameter. 
Only, extending our observations to Eanunculus arvensis, a 
curious and remarkable exception will appear in its pollen- 
grains. These are very rough, have an average diameter of 
^th of an inch, being about twice the size of those of its 
immediate congeners ; and thus, both in form and size, we very 
easily realise a singular difference. In short, here is a plant 
at once known by its pollen-grains. Then, in other sections of 
this same order of the Crowfoots, the pollen-grains are neither 
globular nor rough, but smooth and oval, and with the appear- 
ance of a slit or inflection of the membrane, reminding us of 
the figure of a coffee-berry. This appearance is constant ; but 
in pure water the cell often becomes turgid and globular, when 
the apparent slit vanishes as if it had been originally due to a 
linear fold or partial collapse of the cell-wall, as is certainly the 
case in some other pollen-grains of this shape. But we do not 
see it in those of Ealmnculus arvensis, and some of its near 
allies, although this coffee-shaped pollen-grain is common to 
several different orders of plants, and may be well seen, among 
the Eanunculacese, in Eanunculus Ficaria, Caltha palustris, and 
Trollius Europsea. 
Among Leguminosse, too, this form of pollen is well exem- 
plified in Lotus corniculatus and L. major. Now these are two 
plants which are regarded by some of our most eminent botanists 
as nothing but varieties of one and the same species, “Lotus 
major being only larger in all its parts, from its moister habitat, 
than L. corniculatus.” But our inquiries will show, on the 
contrary, that the pollen-grains of the smallest of these plants 
are the largest ; for in L. corniculatus their average size is 
3 -rd of an inch by yy^-^th, while in L. major, they are about 
a third smaller, measuring only -i^^th of an inch by y-g^^th. 
Thus these two interesting plants may be distinguished from 
each other by the pollen-grains ; as we have figured them, with 
those of some of the Eanunculese, in Dr. Seemann’s “Journal 
of Botany,” for September 1866. 
The significance of the cell-bistory, in the present point of 
view, would be much increased by an exposition of it in the 
plant-tissues generally. But as we cannot do this now, a few 
remarkable examples only will be here noticed. Compare, e.g.^ 
the beautiful radiate or stellate cells of the pith of Juncus con- 
glomeratus, J. effusus, and J. glaucus, with the oval cells of 
the pith of J. squarrosus and J. bufonius ; when the cells of 
the former three species will be seen as an actinenchyma, and 
of the latter two as an ovenchyma, a constant and curious differ- 
