Apbil 13, 1883.] 



SCIENCE. 



287 



Limpopo on the maps, with an historical slietch of 

 the native government of the region, of which Mu- 

 zila, son of Manicussa, is at present the head. After 

 the Zambezi, the Bembe is the largest river of east- 

 ern Africa. Its valley is very fertile, — suitable for 

 the growth of sugar-cane, cotton, etc., — and is well 

 populated. To the northward the country is more 

 healthy for Europeans. Its fine forests of valuable 

 wood contain many elephants, and its saline lagoons 

 are full of hippopotamus; but, "in consequence of 

 the absence of native population, the tsetse-fly is 

 found everywhere through it." In a somewhat ex- 

 alted peroration, the author concludes with, " We 

 have traversed a vast area of the province of Mocam- 

 blque, finding it all most salubrious and excellent for 

 occupation by the white race. It possesses all the 

 conditions to make it suitable for the immigration of 

 millions of Europeans, who will find its soil more 

 fertile than that they have left. It is perhaps the 

 most populous region of all tropical Africa; and its 

 millions of natives, placed in contact with civiliza- 

 tion, will become consumers of innumerable Euro- 

 pean wares;" — (Bol. hoc. geogr. Lisboa,18S2, 336.) 

 W. 51. D. [609 



BOTANY. 



Ice -plant (Mesembryanthemum crystalli- 

 num). — M. Herve Mangon calls attention to the ease 

 with which this plant can be cultivated on a large 

 scale as a source of potash. According to him, the 

 fresh plant contains about half of one per cent of 

 potash. — [Comptes rendus, Jan. S, 1883.) g. l. a. 



[610 



Loss and gain of nitrogen by arable soil . — M. 

 Dehe'rain gives a very interesting account of his ex- 

 periments at the station at Grignon, which may be 

 summarized as follows: the loss of combined nitro- 

 gen which a harvested field sustains is not due ex- 

 clusively to the removal of the crop, but is largely 

 attributable to the oxidation of nitrogenous matter 

 in the soil, and its escape in the form of nitrates in 

 drainage-water. The loss is greatest when the use 

 of fertilizers has been most generous, and it ceases 

 when the fields lie fallow. The reason for the latter 

 is, that then the air penetrates less deeply. The 

 results are quite in accord with those previously 

 reached at Eothamsted. — (Comptes rendus, Jan. 15.) 



G. L. G. [611 



Solar radiation, and assimilative activity. — 



Timiriazefi:', whose experiments upon the action of 

 chlorophyll are of great importance, has lately pub- 

 lished in a short note a few of his more recent re- 

 sults. Quantitatively determined, forty per cent of 

 the amount of solar energy absorbed by a green 

 leaf under the most favorable conditions is convert- 

 ed into chemical work. He calls attention to the 

 usefulness of Langley's bolometer in such investiga- 

 tions. — (Comptes rendus, 'F&h.b.) G. L. G. [612 



The difference bet^mreen the chemical consti- 

 tution of living and dead protoplasm has been 

 further studied by Loew; and the results of the in- 

 vestigation, too complicated for a short abstract here, 

 accord in the main with those previously noticed 

 in this journal. — (Pfluger's archiv, Feb. 12. ) G. L. G. 



[613 



Fertilization of Yucca. — The deliberate polli- 

 nation of Yucca-flowers by a tortricid moth (Pronuba), 

 to insure the production of seed for its young to feed 

 upon, is will known through the publications of its 

 discoverer. Prof. Kiley. From an abstract of a paper 

 read last summer at the Montreal meeting of the 

 American association, by the same observer, it ap- 

 pears that the act of collecting pollen by Pronuba for 



the fertilization of the Yucca " is as deliberate and 

 wonderful as that of pollination. G-oing to the top 

 of the stamen, she stretches her tentacles to the ut- 

 most on the opposite side of the anther, presses the 

 head down upon the pollen, and scrapes it together 

 by a horizontal motion of her maxillae. The head is 

 then raised, and the front-legs are used to shape the 

 grains into a pellet, the tentacles coiling and uncoil- 

 ing meanwhile. She thus goes from one anther to 

 another until she has a sufSciency." The conclusion 

 of Dr. Engelmann, that the apices of Yucca stigmas 

 are not receptive, is confirmed. " The exceptional 

 self-fertilization in Yucca aloifolia, the only species in 

 which it is recorded, is shown to be due to the fact, 

 that, in the fruit of this species, there is no style, the 

 stigma being sessile, and the nectar abundant, filling 

 and even bulging out of the shallow opening or tube. 

 The flowers are always pendulous ; and the pollen 

 falling from anthers can, under favorable circum- 

 stances, readily lodge on the nectar." — (Amer. nat., 

 Feb.) w. T. [614 



Pollination of the fig. — Some light has been 

 thrown on the much-vexed question of caprification, 

 and the relation of the caprifig or Caprificus to the 

 fig-tree, by the studies of Fritz MiiUer and Paul 

 Mayer. It appears that the caprifig is the male fig- 

 plant, as Linne believed, and not a distinct race, as 

 Solms-Laubach has recently maintained. Fig-seeds 

 produce both Caprificus and fig-seedlings. The rela- 

 tions between these two forms of an originally mo- 

 noecious species, and the gall-fly (Blastophagus), on 

 which it now relies for crossing, are very curious. 

 Three broods of the insects each year are brought to 

 maturity in as many crops of flowers of the caprifig; 

 the first two of which are absolutely infertile, while the 

 last does not average one seed to two figs. On arriv- 

 ing at maturity, the wingless males, after escaping 

 from the fruit in which they have developed, seek out 

 other pistils containing females, which, being impreg- 

 nated before their release, afterward escape, and ijen- 

 etrate other young figs belonging to the next crop, on 

 either caprifig or fig-tree, to oviposit. Being dusted 

 with the pollen of the strongly protogynous flowers 

 from which they have come, they pollinate the recep- 

 tive stigmas over which they creep ; but the flowers 

 of the caprifig only are accessible to their ovipositors. 

 As a result of fertilization, the fig-tree ripens its fruit 

 rapidly, and its seeds are soon scattered by frugivo- 

 rous birds; but that of the caprifig never becomes 

 eatable. — ( MiiUer, Kusmos, Aug. 5, 1882 ; Mayer, 

 iHttheil. zool. stat. Neapel, iii. ; Abstracts, Biolog. 

 central-blatt, Nov. 15.) w. t. [615 



ZOOLOGY. 



Coelenterates. 

 The origin of the spermatozoa in Medusae. — 



In a short paper on this subject, Merejkowsky calls 

 attention to the interesting fact, that the matui'e re- 

 production-follicle of Cassiopea or Ehizostoma bears 

 a close resemblance to the same organ of Pelagia 

 during its very youug stages. At a very early stage 

 of development, the immature follicles are almost 

 exactly alike in all three genera; but in Cassiopea 

 they undergo very little change. The mature organ 

 is a simple ovoidal pouch, lined with endoderm-cells, 

 and filled with spermatozoa. According to the broth- 

 ers Hertwig, Pelagia passes through a similar stage 

 long before maturity is reached; but its development 

 in this genus does not stop here, and it finally be- 

 comes a long irregular pouch, the tortuous ramifica- 

 tions of which are interlaced in an inextricable tangle. 

 It is easy to discern that the simple pouches of 



