SCIENCE 



[Vol. LV, No. 1427 



b. The sub-antaretie flora of Tasmania and the 

 alpine regions of New South Wales and Victoria. 



c. The autochthonous flora, practically universally 

 distributed, but especially developed in western 

 Australia. (5) The tropical vegetation of north- 

 eastern Australia is evidently closely related to 

 the floras of New Guinea and the Malay Archi- 

 pelago. (6) The sub-antarctic flora, especially 

 developed in Tasmania and New Zealand, is evi- 

 dently related to the Fuegian flora of Soutli 

 America. It has been the subject of repeated 

 investigation. (7) The autochthonous flora, which 

 comprises a large majority of the Australian 

 plants, is the main subject of the present discus- 

 sion. This flora is supposed to have developed 

 in western Aus.tralia, when it was completely 

 separated from the eastern part of the continent, 

 and to have later spread over the whole continent. 

 The main problem at hand is to discover evidence 

 which will throw light on the origin of this flora. 

 (8) There are some notable correspondences 

 between the flora of South Africa and Australia 

 indicating some former land connection; but as 

 yet no evidence for this has been found, except 

 at a very early period. (9) Gondwana Land, the 

 great southern continent, believed to have existed 

 at the end of the Paleozoic, is supposed to have 

 united South America, Africa and Australia; but 

 a much later connection between South Africa and 

 Australia must be assumed to explain the resem- 

 blances between their present floras, as presum- 

 ably there were no Angiosperms in existence at 

 the period of the supposed Gondwana continent. 

 What is particularly needed is evidence showing 

 the relation of the land masses of the southern 

 hemisphere during the Cretaceous and the Ter- 

 tiary. Especially important is a knowledge of 

 the fossil plants of these periods, from temperate 

 South America, South Africa and Australia. 

 (10) It is possible that when the fossil plants 

 from these regions are thoroughly studied it may 

 prove that in the south temperate zone, as in the 

 corresponding northern latitudes, during the Cre- 

 taceous and much of the Tertiary a practically 

 uniform flora prevailed. Should such prove to be 

 the case, it is probable that the existing floras 

 in the soutli temperate regions are the descendants 

 of this uniform flora, which shut off in these com- 

 pletely isolated areas have become altered to a 

 greater or less extent. Western Australia, the 

 most completely isolated of the southern regions, 

 has developed the richest and most specialized 

 flora. 



The nature of disease, resistance or immunity in 



certain plants: Professor L. E. Jones, J. G. 

 Dickson and J. C. Walker, University of Wis- 

 consin. 



A side effect from the importation of parasites 

 of injurious insects: Dr. L. 0. How'ARD, chief of 

 the Bureau of Entomology, Department of Agri- 

 culture. In the efforts to bring about a natural 

 biological control of injurious insects in many 

 parts of the world, an increasing amount of work 

 is being done by the entomologists of the different 

 nations to bring into their own countries the for- 

 eign parasites of foreign insect pests that have 

 been accidentally introduced and have become 

 established. In the course of this work, the moti- 

 vating idea is the control of the specific introduced 

 pest; but it has developed in many instances that 

 the introduced parasite is not specific to the intro- 

 duced host, but attacks allied native injurious 

 species. The speaker described a number of these 

 instances in America. These findings oifer a very 

 strong iidditional aigument in favor of the prose- 

 cution of woik of this character. 



Mitochondrial bodies in the spermatogenesis of 

 Chortliippus Cvrtipennis (Scudd.) : Dr. E. L. 

 Mark and L. C. Wyman, Harvard University. 

 Numerous bodies found in the apical (Verson's) 

 cell of the testicular follicle, as well as in the 

 primary and secondary spermatogonia, the first 

 and second spermatocytes, and the spermatides of 

 this grassJiopper are described as spheroidal 

 structures composed of two substances, a central 

 nonstainable core and a deeply stainable mantle 

 or cortex. The appearance of the bodies when 

 stained is that of a vesicle with clear contents 

 and stained wall of no great thickness. They 

 occur in a single large cluster, or in smaller 

 groups, and are accompanied by finely granular 

 deeply staining cytoplasmic substance. These 

 vesicle-like bodies are believed to be mitochondria, 

 and are genetically continuous from the primary 

 spermatogonium to the formation of the sperma- 

 tid. In the metamorphosis of the spermatid into 

 a spermatozoon their history has been traced till 

 they break up into minute granulations envelop- 

 ing the axial filament of the thread-like mature 

 spermatozoon. At each of the cell divisions of 

 spermatogenesis the vesicles are collected into a 

 ring at the periphery of the equatorial region of 

 the spindle figure, and soon after the chromosomes 

 divide and separate, in the metaphase of cell divi- 

 sion to form two daughter nuclei, it is found that 

 these vesicles are likewise arranged in the form of 

 two parallel rings— each containing about the 

 same number of vesicles — one on each side of the 



