NATURE 



[November 14, 1912 



temperaUire distribution in the atmosphere over 

 England, with some remarks on the general and 

 local circulation (this being an abstract of a paper 

 appearing in the Philosophical Transactions of the 

 Roval Society), and with total and partial correla- 

 tion coefficients between sundry variables of the 

 upper air. The main conclusions, as we gather 

 from Dr. Shaw's preface to this memoir, are that 

 the upper regions of cyclonic areas are colder 

 than those of anti-cyclonic areas, and that the 

 temperature up to the stratosphere varies in the 

 same direction as the pressure at the surface, and 

 that a close relation exists between the five 

 quantities — pressure at ground level, mean tem- 

 perature up to nine kilometres, pressure at nine- 

 kilometre level, height of troposphere, and tem- 

 perature of stratosphere. Illustrations are given 

 of progessive changes in cloud formation. 



In No. 3, Mr. G. W. Walker, superintendent 

 of Eskdalemuir Observatory, which has become 

 answerable to the Meteorological Office, gives a 

 graphical construction for (the epicentre of an 

 earthquake ; and in No. 4 Mr. R. Corless, who, 

 as Dr. Shaw's scientific secretary, is following in 

 the footsteps of such men as Dr. G. C. Simpson 

 and Mr. Ernest Gold, deals w'ith the radiation 

 records obtained in 191 1 at South Kensing'ton, 

 together with a comparison between them and 

 the corresponding absolute observations of radia- 

 tion made at Kew Observatory. We need only 

 remark that it would be more satisfactory for 

 some purposes if a more direct comparison could 

 be made than one between a vertical instrument at 

 one station and a total radiation instrument at 

 another station, operated for only part of the time. 

 Mr. Corless himself emphasises this difficulty, but 

 apart from the comparison with Kew, the actual 

 observations are of great interest, and show 

 among other results the inadequacy of the sun- 

 shine instrument as a radiation recorder. 



W. W^ B. 



THE BIOLOGY OF THE FIG-TREE AND ITS 

 INSECT GUEST.^ 



WE take advantage of a recent treatise on fig- 

 culture *o enlarge and correct what has 

 hitherto been taught about the biology of the fig- 

 tree and its insect guest, Blastophaga. Our new 

 information is drawn from Dr. Ruggero Ravasini's 

 "Die Feigenbaume Italiens " (Bern, 191 1), which 

 gives the results of a prolonged study made in 

 Italy. The research has been directed by. Prof. 

 A. Tschirch, of Bern ; for the detailed observa- 

 tions and experiments we have to thank Dr. 

 Ravasini, who, in addition to his scientific attain- 

 ments, enjoys the advantage of being an Italian, 

 and therelDy better able to win the confidence of 

 Italian fig-growers. Fig-cultivators and all 

 biologists who make a special studv of the fig- 

 tree will, of course, betake themselves to the 

 original treatise, which is clear, interesting, well- 

 illustrated, and not too lengthy. We shall here 



1 "Die FeigenbHume Italiens und ihre Beziehungen zueinander." By Dr. 

 Kviggero Ravasini. Pp. 174 + 6. (Bern: Max Drechsel, 1911.) Price 



NO. 2246, VOL. 90] 



address ourselves to those biologists for whom a 

 less complete exposition will suffice, at least for 

 the moment. 



The structure and life-history of the fig-tree 

 have been modified by long-continued cultivation ; 

 and in order to simplify the presentation of the 

 facts, we shall first describe the reproductive 

 process in the wild fig-tree, which still maintains 

 itself in Italy, probably also in all fig-growing 

 countries where the ground is not too closely 

 occupied by cultivation. 



The wild fig-tree is monoecious, its unisexual 

 flowers being- collected into mixed inflorescences. 

 In remote ancestors of the figs the head may 

 have taken the usual flattish or convex form. 

 Dorstenia, an allied plant, which is now and then 

 seen in hothouses, bears a crowd of small greenish 

 flowers on a flattened disc about an inch wide. 

 In a fig the edges of the disc close in upon the 

 flowers, and we get a hollow, pear-shaped 

 receptacle lined with minute, crowded, unisexual 

 flowers. The opening is not only narrowed, but 

 further obstructed by outward-pointing scales. 

 During ripening the wall of the receptacle becomes 

 thickened, and the central cavity almost dis- 

 appears. In Dorstenia the small fruits are shot 

 out by the turgidity of the wall ; in the figs the 

 wall may become eatable, and promote the dis- 

 persal of the seeds in another fashion. 



The wild fig-tree bears three different kinds of 

 inflorescence, according to the season of the year. 

 There is a spring inflorescence, bearing male and 

 sterile female flowers ; a summer inflorescence, 

 which bears only fertile females ; and a ivintering 

 inflorescence, which bears only sterile females. 

 Sterility here results from the adaptation of 

 female flowers to the nutrition of fig-wasps 

 (Blastophaga) ; the sterile flowers are hence called 

 gall-flowers. In the cultivated fruiting fig-tree 

 sterile pistillate flowers of another kind occur. 



The process of pollination of the fig by Blasto- 

 phaga is comparatively familiar, but it may be 

 briefly described here to save the necessity of 

 reference to books. Blastophaga is a small 

 Chalcidid hymenopterous insect. The male is 

 wingless, and the female (which alone passes 

 from one inflorescence to another) winged. In 

 spring, impregnated females issue from the 

 wintering inflorescence and fly to the spring- 

 inflorescence. Here they lay eggs in the gall- 

 flowers, one egg to each flower, and from these 

 eggs both male and female flies proceed. When 

 full grown, the male crawls sluggishly about until 

 he becomes aware of the presence of a female 

 still enclosed within the ovary of a gall-flower. 

 Then he biles a hole in the ovary, passes in the 

 tapering, pointed end of his abdomen, and effects 

 his purpose. Since the male rarely quits the in- 

 florescence, he has no need of wings or eyes ; 

 accordingly there are no wings, and the eyes arc 

 poorly developed ; even the antenna; are small 

 and few-jointed ; the mandibles, however, and 

 two of the three pairs of legs, are powerful. 



The winged female after impregnation bites off 

 the top of the ovary, and makes her way into 



