( '9fi) 



Botany. — "On plants vshich in the natural state have the character 

 of eversporting varieties in the sense of the mutation theory." 

 By Dr. W. Bdrck. (Communicated bv Prof. J. W. Moll). 



(Communicated in tlie meeting of Marcli 31, 1906). 



An investigation ot the causes of Cleistoganiy ') showed that: 1 

 plants with closed flowers originated bv mutation from plants with 

 chasmogamic flowers and 2 that they occur in the natural state, 

 partly as constant, partly as ever-sporting varieties. 



In the course of this investigation the question arose whetlier other 

 wild-growing plants do not also lia\e the character of ever-sporting 

 varieties. 



Especially those plants were thought of that have bisexual and 

 unisexual flowers in one and tlie same individual or in which by 

 the side of bisexual, unisexual individuals are found and also those 

 plants among the dioecious ones that possess rudimentary stamens or 

 ovaries, from which may be inferred that they originated from plants 

 with bisexual flowers. 



The agreement between unisexual, cleistogamic and tilled flowers 

 pointed to the same origin, while the resemblance in the manner 

 in which unisexual flowers occur among the hermaphrodite ones and 

 closed tlowers among the chasmogamic ones, justified the assumption 

 that in the monoecious and dioecious as well as in the cleistogamic 

 we have ever-sporting and constant varieties. 



This summer I tried to confirm this conception in a twofold manner, 

 firstly by cultivating the gyno-monoecious Satureja hortensis and 

 secondly by studying the different forms in which one and the same 

 andro-monoecious Umbellifer can occur in nature with regard to the 

 number of male flowers in proportion to that of the bisexual ones 

 and to the place \vhicli the male flowers occupy on the principal 

 and secondary axes. 



To the results of the culture experiments I shall return afterwards 

 when I shall have had an occasion to repeat these experiments on 

 a larger scale and with more species. I will here only mention that 

 they showed tliat a gyno-monoecious Satureja hortensis begins its 

 period of flowering with producing bisexual flowers only, that not 

 until later, when the plant has grown stronger, a few female flowers 

 appear among the bisexual ones, that their number gradually increases 



') Die Mutation als Ursache tier Kleistogamie. Recueil des Travaux Botaniques 

 Néerlandais Vol. II. 1905. 



