LINNEAN SPECIES IN OUR DAYS 293 



parents, tlie descendants produce continually varying forms ; Linne 

 does not acknowledge these as species, but supposes that they are 

 hybrids. Thus beyond tlie varieties ex loco and the constant varieties, 

 Linne observed still a third kind, the hybrids (Fuind. fructif. p. 13). 



Ltnne and Darwin. 



Darwin studied the struggle for existence. The influence of 

 environment is very great. Nature decides on the fate of all forms. 

 A great many new forms ai-e too weak for the struggle and disappear, 

 but some are stronger than the parents and supplant them. Of 

 course, the same law must prevail both for new constant varieties and 

 for hybrid forms. 



Linne spoke of " helium omnium in omnes." He observed the 

 immense number of seed and brood that the organisms produce ; and 

 found in this Nature's method of preserving living organisms in the 

 former state. Darwin went much deeper and discovered an important 

 biological law that I like to call " Darwdn's law," by which I mean 

 the different influences of environment on different forms. 



Unfortunately Darwin did not know of Linne's experiments with 

 the constant varieties. He regards the varieties as beginning new 

 species, influenced b}^ the struggle for existence. We do not now^ 

 assume tliat natural selection is able to create new qenes. But when 

 occasionally new genes ov new combinations of hybrids appear, Nature 

 decides on them, and in this way upon the development of flora and 

 fauna in every country. 



If in cultivation new varieties appear spontaneously, they will 

 often be in more favourable conditions than in a wild state. Protec- 

 tion, e. g. of (Enofhera Lamarckiana, is able to save many forms 

 that are not fltted for the struggle for existence. 



LiNN^ and Mendel. 



Linne crossed two species of Tragopocfon and raised a fertile 

 hybrid. In his garden sometimes new^ hybrids appeared spontaneously. 

 From his studies of Peloria (1744) his mind was constantly led to 

 hybrids as the origin of new species. He formed the theory that all 

 new species originate from crosses, and that in this waj^ the whole 

 development of plants originates from onl}^ one species in any natural 

 family. He often appeals to scientists to investigate the question 

 earnestly : — 



" Per banc hypothesin quisque cordatus botanicus admonetur, ut 

 ad ortum specierum posthac soUicite attendat et experimenta instituat, 

 utrum casu et arte produci queant ; si hoc obtinetur, clavem habe- 

 bimus hue usque desideratam fundamenti fructificationis a priori, a 

 posteriori hactenus tantum inductam et exemplis confirmatam." " Si 

 interim hjBC sententia vel hypothesis recipiatur, clavis adest funda- 

 menti fructificationis a priori, quse omnes aperit januas claussas in 

 svstemate vegetabili. et sine qua introitum a priori frustra quaesiveris" 

 (Fundam. fructif. 1762, p. 22). 



A century passed away, and the expected '* cordatus botanicus 

 appeared." By his analysis of species Mendel began a new era in 

 Biology. 



