272 



SCIENCE 



[N. S. Vol. XXV. No. ( 



multinucleate (forty have been observed) 

 as they grow in numbers over the sporo- 

 phyll from their place of deposition, some- 

 times 3 em. from the micropyle. Some 

 penetrate the integument instead of enter- 

 ing the micropyle. There is no differentia- 

 tion of a tube nucleus and only a single 

 generative cell is present. For these rea- 

 sons the Araucarieffi are considered by the 

 author as proto-siphonogamic. There are 

 indications also of a non-specialized em- 

 bryogeny, intermediate in character be- 

 tween that of the cycads and of Ginkgo. 



The Flowering Period of a Hyhrid 

 Opuntia: F. E. Lloyd, Desert Botanical 

 Laboratory. 



A Study of the Leaf-tip Blight of Draccena 

 fragrans: John L. Sheldon, West Vir- 

 ginia Agricultural Experiment Station. 

 (Eead by request before the Botanical 

 Society of America.) 



Teacy E. Hazen, 

 Secretary pro tempore 



SCIENTIFIC BOOKS 

 Becherches experimentales sur la Sexualite 



des spores chez les Mousses dio'iques. Par 



El. et Em. Maeghal. Mem. couronnes CI. 



Sc. Ac. roy. Belgique, 2, I., 1906. 



" A considerable number of plants are 

 known in which a single egg gives rise by 

 division to more than a single individual. 

 Experimental investigations are demanded to 

 determine if these individuals are always 

 necessarily of the same sex." In response to 

 this subject, thus recently proposed by the 

 royal academy of Belgium, the Marchals have 

 published the results of an interesting series 

 of experiments on three dioecious mosses. Bar- 

 hula unguiculata, Bryum argenteum and 

 Ceratodon purpureus. Sowings were made 

 from individual sporangia of these three spe- 

 cies and, in the mixed growth resulting, both 

 male and female plants were obtained. The 

 conclusion thus reached that the capsule in 

 these species contains both male and female 

 spores was confirmed by sowings from single 



spores. Of five spores from a single capsule? 

 of Bryum argenteum, three gave rise to pro-- 

 tonemata producing male and two to thosse 

 producing female plants. Similarly, of seven 

 single-spore sowings from a capsule of Bar^ 

 hula unguiculata, three spores produced male- 

 and four produced female plants exclusively^ 



Secondary protonemata, obtained by regen- 

 eration from stem, leaf or pieces of proto- 

 nemata, as well as by germination of gemmse^ 

 were of the same sex as the plants from whicb 

 they were derived. 



Attempts to influence the sex of protone- 

 mata by subjecting them to different external 

 conditions were entirely unsuccessful. Tine- 

 effects of the following factors were tested s 

 (1) Illumination. Cultures in strong and i» 

 weak, diffuse daylight and under red an^ 

 under orange-colored glass. (2) Temperature^ 

 Three grades of temperature from 10 to 2Y' C» 

 (3) Humidity. Cultures in saturated atmos' 

 phere and in an atmosphere as dry as consist- 

 ent with growth. (4) Nutrition. A clayey 

 sandy soil watered with solutions of different 

 chemical composition. The nutrition experi- 

 ments would have been more satisfactory if 

 a substratum had been used which alone was 

 not capable of producing an abundant moss- 

 vegetation as was the sandy clay employed^ 

 The experiments are sufficient, however, to» 

 show that the gametophytes of the mosses* 

 tested are strictly dioBcious. Writers on the- 

 mosses have claimed that in dioecious species- 

 both sexes arise from the same protonema, but" 

 heretofore no careful study of the sexual dif- 

 ferentiation in the mosses has been under- 

 taken. Marchal's important experiments il- 

 lustrate the value and necessity of the cultural 

 method of investigation. 



These three species of mosses studied by 

 Marchal and the liverwort Marchantia polp'^ 

 morpha investigated by the reviewer (Bot, 

 Gaz., XLIL, 171, Sept., 1906) are the only 

 dioscious bryophytes for which the sexual' 

 character of the sporophyte is known. That 

 these forms which are dioecious in the gameto- 

 phyte are all hermaphroditic in sporophyt©' 

 (heterothallic and homophytic according to *> 

 more precise terminology \^Bot. Qaz., I. c.])' 

 does not prove that this is the universal type? 



