484 ^ Trmisactions of the Society. 



of pollen. For wind -borne pollen it is also specially suitable. Even 

 when pollen has assumed other forms, it sometimes after reaching 

 the stigma absorbs moisture and resumes the spherical shape. 



Moreover, while when the pollen grains are few the pollen tends to 

 assume an elliptic form, generally with longitudinal, but sometimes 

 with a cross furrow or furrows, on the other hand when the pores 

 are numerous the pollen retains a spherical shape. 



Spherical pollen falls into two divisions — that which is smooth 

 and that which is spiny. Speaking generally, that which is smooth 

 is borne by the wind, that which is sjDiny is adapted for carriage 

 by insects. 



There are, however, exceptions to this rule. Some species of 

 Corydalis have spherical and almost smooth pollen, but they are 

 perhaps as a rule self-fertilizing. The Cistacese generally have 

 ellipsoid pollen, but in some species (C. laurifolius and C. clusii 

 for instance) it is globular. 



Indeed, between the elliptic and the spherical pollen we find 

 every gradation. The species of Linum (Flax) have an ellipsoid 

 pollen ; in some, however, it is very tumid, and in L. perenne mainly 

 globular. 



Pollen ichich is spherical and smooth. 



C. C. Sprengel in his remarkable work * gives as characteristics 

 of wind flowers — 



1. The large quantity of pollen which is necessary on account 

 of the great waste. 



2. The absence of viscidity, or as he terms it the dryness, which 

 enables it to be more easily carried off by the wind. 



3. The mobility of the anthers, which tends in the same 

 direction. 



4. The tendency to early flowering, so that the leaves do not 

 prevent the free access to the stigma. 



He does not refer to the form of the pollen, or that of the 

 pistil, which, however, are also characteristic. 



Kerner also in his charming work, and Knuth in his valuable 

 handbook, f refer to the above characteristics, but do not mention 

 the form. 



Knuth I gives the following list of spring flowering wind 

 flowers : — 



Corylus avellana. JJlmns campesiris. 



Ahius ghitinosa. U. montava. 



A. iyicana. U. effusa. 



* Das Entd. Geheimniss der Natur., Christian Konrad Sprengel, 1793. 



t Handbuch der Bliiten Biologie. 



\ Handbuch der Bliiten Biologie, i., p. 86. 



