su 



W. PEAESON ON THE MOKPHOLOGY OF 



group is obscure, and it is liiglily improbable that its complete elucidation will establish 

 the view that they represent a simple series. The statement contained in No. 2 is no 

 doubt true, but has it necessarily any bearing upon the point at issue ? The conditions 

 which influence the development of the vegetative organs do not necessarily affect the 

 reproductive parts. An angiospermic parasite, for example, frec^uently shows extreme 

 reduction in all parts of the plant-body save in those concerned with reproduction, 

 which may, indeed, be of a highly specialized character. The fact that the archegonia 

 of the imperfect female flowers of Ephedra campylojpoda show no signs of reduction is 

 not conclusive, if true. An argument based upon Ephedra must almost certainly apply 

 to Gnetum and Welwitschia, In the latter, sporogenous tissue is not organized in the 

 so-called hermaphrodite flower ; in the former, gametes do not appear in the incomplete 

 female flower. The female flower of Ephedra campylopoda is less incomplete than that 



F 



of either of the other two genera, but if reduction can account for the one it must 

 explain all. The last two points are of less importance. If an Angiospermic species 

 with polygamous flowers may be held to be descended from a more primitive form with 

 hermaphrodite flowers, a similar explanation of the occurrence of female, male, and 

 more or less hermaphrodite inflorescences or spikes in the Gnetales is not ruled out. 

 Since the date of Wettstein's paper it has been shown that E. campylopoda is ento- 

 mophilous*; the same is true for Welicitschia ^ , and not improbable for Gnetum%. 

 In all cases it is probable that the ovule of the " hermaphrodite " spike or flower has 

 become specialized in connection with insect-pollination. This specialization is much 

 more likely to have occurred through the reduction in some or all of the parts of 

 a primitively functional hermaphrodite flower than by " progressive mutation." In the 

 latter case the fact that a new and previously functionless structure adapted to attract 

 insects bears so curious a resemblance to a functional female flower would be difficult 

 to explain. 



Strasburger § discussed the question fully and, at least for Welicitschia and Ephedra, 

 arrived at the conclusion that the female flower in each case represented an advanced 

 stage in the reduction of a primitive hermaphrodite flower, and that the pseudo- 

 hermaphrodite flower of Welicitschia represents an intermediate stage passed in the 

 course of this reduction. While it is not impossible that the actual course of events has 

 been more complicated than is here suggested, Strasburger's view that the existing 

 structures are the result of a process of reduction seems to be in closer accord with 

 the facts than the contrary opinion of Wettstein || . 



Both the female and the pseudo-androgynous spikes of Gnetum Gnemon in the 

 specimens under notice very frequently bear a single terminal ovule ; this was also 

 recorded by Strasburger^. This fact, together with the occasional reduction of the 

 male spikes to two nodes separated by an internode {G. Bucholzianum **) and the 

 presence of " a ring of complex groups of vascular strands arising from the branches in 



* Porsch, 0., 1910. t Pearson, 1909. 



t Karsten, 1893 ; Lotsy, 1899, &c. § Strasburger, 1 



Lienier 



f 



*» Pearson, 1912. 



