588 



NATURE 



[October i6, 1890 



and ending with another small group {Neomoj-phe) 

 remarkable for having di- or tri-androus male flowers, 

 and the receptacles (fruit) borne in clusters, often very 

 large, on the trunk and branches, sometimes at the very 

 base of the trunk. 



Curiously enough, although the other five groups or 

 sections, into which King divides the genus Ficus, are 

 all represented among the additional species from New 

 Guinea, neither the oldest nor the newest is ; but both 

 are represented there by previously known species, and 

 the Neomorphe by some of the most remarkable of the 

 genus. Thus, imperfectly as the flora of New Guinea is 

 known, there are indications of great age and variety. 

 Noteworthy among the species figured in the present 

 work is Ficus hesperidiiformis, King, belonging to 

 the section Urostigma, which is characterized by 

 having male, female, and " gall-flowers " intermixed in 

 the same receptacles. Ficus hesperidiifonnis resembles 

 the familiar india-rubber tree, F. elastica, but the leaves 

 are larger and the receptacles (fruit) very much larger ; 

 the ripe dry ones resembling small oranges, hence the 

 specific name. 



Dr. Cunningham's memoir on the fertilization of Ficus 

 Rflxburghii is an interesting and important contribution 

 to the subject of reproduction, inasmuch as he arrives at 

 some rather startling conclusions with regard to the 

 plant in question. 



The relations between certain insects, parasitic in the 

 receptacles of the fig and caprifig, and in various other 

 species of fig, and the fertilization of the flowers, has 

 been investigated in recent times more especially by Dr. 

 G. King, Mr. Fritz Mueller, and Count Solms ; and 

 particulars of their results, or conclusions, have been 

 given from time to time in Nature (vols, xxvii. 

 p. 584, xxxvi. p. 242, and xxxix. p. 246). Neverthe- 

 less it may be well to repeat here some of the princi- 

 pal conditions and phenomena of the flowers of figs. 

 In the first place^ it may be noted for unbotanical 

 readers that the flowers of figs are very small and 

 crowded all over the interior of the receptacle or fruit. 

 Further, that the wall or substance of the receptacle is 

 continuous and closed, except at the apex, where it is 

 provided with a number of closely overlapping scales, 

 rendering ingress, and egress, without eating its way, 

 impossible to any but a very minute insect. I say, with- 

 out eating its way, because much depends upon whether 

 insects can reach the interior of the receptacles and at 

 the same time carry pollen with them ; and writers on 

 the subject, so far as I am aware, have not considered 

 the probabilities of the earlier visiting-insects thus opening 

 a channel for those following. I have also, in another 

 place, suggested the possibility of the scales at the mouth 

 of the receptacle being loosened at the receptive period 

 and Mr. C. B. Clarke tells me that he has actually 

 observed this to be the case. 



The flowers are of four kinds — namely, male, female, 

 neuter, and gall ; and they are variously associated, or 

 separated, in different species of Ficus. There are 

 indeed five kinds of flowers if we include the pseudo- 

 hermaphrodite flowers of the group Palceomorphe. In 

 the cultivated fig {Ficus Caricd), the flowers are almost 

 invariably all female ; and the male flowers of this species 

 are borne by the " caprifig " of the south of Europe and 

 NO. IC94, VOL. 42] 



Western Asia. Associated in the same receptacles with 

 the male flowers, and covering the whole of the inside 

 except a ring near the top, are the so-called gall-flowers. 

 Structurally they are female, but instead of bearing seed 

 they nourish the larva of an insect, and the perfect 

 females of this insect are supposed to convey the pollen 

 of the male flowers to the receptacles containing female 

 flowers, the ovules of which are thereby fertilized. The 

 presence of insects in figs seems to be general in the very 

 numerous (500 perhaps) species spread all over the tropical 

 regions of the earth ; and the commonly accepted theory 

 is that these insects, in return for the shelter and nourish- 

 ment received, convey the pollen from the male to the 

 female flowers, so that the association is mutually bene- 

 ficial. At least this was the theory of Solms and Fritz 

 Mueller. In the introduction to his monograph of the 

 Asiatic figs, Dr. G. King says :— " The exact way in 

 which the females are pollenized is a matter on which I 

 cannot pretend to throw any light. I can only state the 

 problem." Yet a little farther on he states that there can 

 be no doubt that the insect developed in the gall-flowers in 

 some way conveys the pollen of the males to the females 

 in other receptacles, though he found it difficult to under- 

 stand how this could be effected ; and he informed the 

 writer that he had never discovered the slightest evidence 

 of the process, beyond the fact that seeds were formed. 



At the instigation of Dr. King, Dr. Cunningham has 

 thoroughly investigated the phenomena of fertilization in 

 Ficus Roxburghii, and he arrives at the conclusion that 

 pollen is never, or exceedingly rarely, conveyed to the 

 female flowers, though good seed is abundantly matured. 



Ficus Roxburghii is perfectly dioecious — that is, the two 

 sexes are produced on different trees ; and the fruit is 

 borne in large clusters on the thicker branches and trunk 

 often at the very base of the same, and extended on the 

 ground.^ The receptacles are similar in shape to those 

 of the common fig, and from two to three inches in 

 diameter, or sometimes nearly four inches ; and the 

 flowers are proportionately large, so that they are easily 

 examined. It may be mentioned, too, that this species 

 belongs to King's section or sub-genus Neomorphe, which, 

 in our opinion, exhibits the latest stage in the evolution 

 of the genus. 



It would occupy too much space to follow Dr. Cunning- 

 ham through his investigations, but it will suffice to give 

 some extracts from his concluding remarks : — 



"There can be little room for doubt that the phenomena 

 indicate that, while the development of embryos in the 

 female receptacles of the tree is essentially connected with 

 the access of the insects to the receptacular cavity, it is 

 yet normally independent of the introduction of pollen by 

 their agency. The fact that the access of a single insect 

 or of a pair of them only is sufficient to determine the 

 development of ten or twelve thousand embryos, is in 

 itself almost conclusive against the occurrence of any 

 ordinary process of pollination. The obstacles through 

 which a passage has to be forced ere the receptacular 

 cavity is reached are of such nature and amount as to 

 render it almost inconceivable that pollen should be 

 introduced in sufficient quantity, and there is at the same 

 time an absolute want of evidence to show that such 

 introduction takes place. I have carefully examined very 

 many receptacles at various periods shortly after access 



' A photograph of a tree in fruit forms the frontispiece to the first voIuitj 

 of the " Annals of the Calcutta Garden." 



