S26 MONOGRAPH OF THE BRITISH SPECIES OF EUPHRASIA. 



their nectaries smaller, they are thus provided for autogamy. 

 Mliller gives the following names of insects he has observed to visit 

 E. Bostkoviana and E. stricUi : — Bombus agrorum ; B. pratorum ; 

 Apis melUfica ; Nomada lateralis ; Systrechus sulphureus ; Syrpbus 

 sp. ; Melithreptus tzeniatus. Prof. Wettstein has observed the 

 following visiting E. Rosth-oviana : — Bombus pratorura ; Melano- 

 stoma barbifrons ; Halictus cylindricus. 



The Nectary is minute in all the species, and is situated at the 

 back of the ovary on the anterior side. 



The Fruit cousists of a two -celled many-seeded capsule in all 

 the European species ; in form it is elliptic or ovate, truncate or 

 rounded, entire or emarginate, and tipped with the base of the 

 style ; its length with respect to the calyx varies in different 

 species, and consequently offers specific characters. It is usually 

 furnished with straight and erect long or short hairs at the sides and 

 apex, and with additional shorter adpressed hairs. The dehiscence 

 is loculicidal and two-valved. 



The Seeds are numerous in the European species ; they are 

 reduced to two in each cell in some Extra-European species ; they 

 are pendulous, longitudinally furrowed, and narrowed at the apex ; 

 they preseut no satisfactory specific characters. With regard to the 

 dispersion of the seeds, as there is no special provision for this in 

 the seeds themselves. Prof. Wettstein considers that the feet of 

 birds are effective as agents in their dispersion ; also the elasticity 

 of the withered or dead stem and branches is potent for dispersal, 

 when these are moved by the wind or by passing animals. The 

 seeds being very light, both wind and water are also doubtless 

 powerful agents for dispersal. 



As regards any marked difference in anatomical structure between 

 the species, Prof. Wettstein remarks that he finds greater anatomical 

 differences in the same species when under different conditions of 

 locality, environment, &c., than are to be found between different 

 species. The anatomical character of the stems of the perennial 

 species naturally differs from those of the annual species. 



The Evolution or Formation of Species. 

 A chapter of the Monograph is devoted to the question of the 

 origin of the species, and here it is stated that the method of 

 induction has been too much pursued, whereas that of deduction 

 has been too little considered. As important factors in the formation 

 of species in the genus Euphrasia Prof. Wettstein gives the fol- 

 lowing : — 1. Hybridity; 2. Varied Climatic Conditions; 3. Arrest 

 of Periods of Vegetation. He does not exclude other factors in 

 the production of new forms or species, and he alludes to the 

 survival of the fittest as one of these. We will take in order the 

 three factors given above. 



1. Hybridity. — A hybrid may become at once a new and con- 

 stant species or an intermediate form. The result may be that the 

 offspring will be intermediate between the parents, with greater 



