10 Notes on Pollen. By Worthington G. Smith. 
fairly constant in size and form in each botanical species of plant, 
but in long-cultivated garden varieties and hybrids the pollen shows 
a great tendency to vary. 
The true form of pollen can only be seen when it is perfectly 
fresh and dry, at the time when it is naturally shed from the 
anther. If placed in water or glycerine for microscopical examina- 
tion, the shape of the grain at once changes, commonly to a 
spherical form. Sometimes on drying the grain will return to its 
original shape, but more frequently it does not do so. A great 
number of Bauer’s drawings, preserved in the herbarium of the 
British Museum, are taken from grains which have been immersed 
in fluid, and so the drawings cannot be implicitly depended upon. 
Mr. A. W. Bennett suggests that plants may be roughly 
divided into two classes—the class which has the pollen carried to 
the stigma by the agency of the wind, and the class which receives 
the pollen through the agency of insects. The first class is said, as 
a rule, to have flowers without ornamental form or beauty of colour, 
and unfurnished with odours ; the latter class is said to have bright 
coloured and more or less scented flowers, attractive to insects. 
The pollen-grain in the first class is said to be as a rule plain in 
form and easily carried by the wind; in the latter spiny or fur- 
nished with protuberances or furrows, to aid in its attachment to 
the limbs and bodies of insects. Generalizations are always dan- 
gerous, especially when made on a large scale, but in this mstance 
Mr. Bennett’s suggestion is undoubtedly supported by a large 
number of facts; there are, however, some striking exceptions. 
It is never safe to judge of the character of pollen from a few 
grains shaken out of a corolla, as sometimes the interior of flowers 
will be found covered with pollen belonging to many different 
flowers. This is caused by the visits of flies, bees, and other 
insects, with pollen from various plants dusted over their bodies. 
Numerous natural hybrids arise from the visits of these pollen- 
dusted insects, and it is quite impossible to keep some garden 
varieties distinct on this very account. The ornamental Gourds of 
our gardens form a case in point. 
In the genus Ginothera most of the pollens are large in size, 
and the grains are more or less attached to each other by fine viscid 
threads. The threads of necessity get entangled on the limbs 
of insects, and so the pollen is carried about and transferred in 
masses. One of the largest pollens known to us is that belonging 
to nothera macrocarpa (Fig. 1, Plate CLXVII.). A second 
member of the Onagrad family is illustrated in Godetia Whitneyi, 
in Fig. 2; whilst a third, Clarkia pulchella, is shown in Fig. 3. 
One of the smallest pollens seen by us in the Onagrad family is that 
belonging to Circwa alpina (Fig.4). Associated with these pollens 
in the anther it is common to find groups of free crystals or raphides. 
