FEBEUAltT 25, 1916] 



SCIENCE 



287 



cerned directly with the transmission of hereditary- 

 characters, these bodies are to be looked upon as 

 representing hereditary substance. They do not 

 arise from the nucleus. Whether the term chondri- 

 osomea should be applied to the organs in ques- 

 tion is left an open question. 

 The Nature of the Cell Plate: C. H. Fakb. (In- 

 troduced by R. A. Harpek.) 

 A study of quadripartitiou of the pollen-mother- 

 cells of a number of dicotyledons, especially Nico- 

 tiana, in which the cell-division appears to be ac- 

 complished without the organization of a cell-plate, 

 but by furrowing as in the division of animal cells. 

 The conditions under which the cells exist were 

 found to approach more closely to those of the 

 typical animal egg than the typical plant cell, 

 namely: the absence of rectilinear cellulose cell- 

 walls; the presence of a mucilaginous matrix, 

 formed by the gelatinization of the walls; the loose 

 disposition in the anther; the spherical form; etc. 

 This suggests a physico-chemical interpretation of 

 the cell-plate, that is, an accumulation of a salt in 

 the equatorial plane between two nuclei. This salt 

 remains in solution if the cell enlarges in response 

 to the osmotic pressure generated by the salt. If, 

 however, the cell can not enlarge either the salt is 

 precipitated or attains such a concentration that the 

 colloids about it are coagulated, thus forming the 

 cell-plate. This conclusion is supported, not only 

 by the present investigation, but by the absence or 

 obscurity of the cell-plate in the algs and fungi, 

 and by the presence of equatorial structures in 

 many encysted and inerusted animal cells. 

 The Life-History of Thraustotheea, a Peculiar 

 Water Mold: W. H. Weston. 

 In a study of Thraustotheea clavata (DeBary) 

 Humphrey, an unusual form hitherto recorded only 

 three times, twice from Germany and once from 

 America, the following facts .were ascertained: 

 (1) The process of sporangiospore formation eon- 

 forms to the usual saprolegniaceous type. (2) 

 The genus is, however, unique among the Sapro- 

 legniacese in that dehiscence of the sporangium is 

 effected through rupture of the wall as a result 

 of swelling of the non-motile sporangiospores 

 within. The fragility of the sporangium wall, 

 moreover, has been greatly over-emphasized. (3) 

 In their further development the sporangiospores 

 may give rise to zoospores, germ tubes or dwarf 

 sporangia. (4) The zoospores are grooved, later- 

 ally bi-eiliate, and of a characteristic shape that 

 can not adequately be described by the terms 

 "reniform" or "bean-shaped" that are generally 



used in this connection. (5) Gemmje are formed, 

 but represent merely a transient resting-state in- 

 duced by unfavorable environmental conditions. 

 (6) In the development of the sexual structures 

 certain phenomena seem to justify the assumption 

 that the formation of antheridia is dependent on 

 contact of the antheridial filaments with th« 

 oogonia; and that oospore formation is, under 

 normal circumstances, definitely correlated with 

 the presence of antheridia on the oogonia. (7) In 

 germination the oospores send out hyphs which 

 either, after limited growth, form sporangia or 

 give rise to extensive mycelia, the type of de- 

 velopment depending on the amount of nutriment 

 present. (8) In its structure and development the 

 fungus shows a resemblance to Achyla that, in the 

 opinion of the writer, is sufficient to entitle it to a 

 systematic position near the latter genus rather 

 than near Viotyuchus. 



The Emhryogeny of Stangeria: Charles J. Cham- 

 berlain. 



More than one sperm frequently passes through 

 the neck of the archegonium, but it is extremely 

 rare for more than one to enter the egg. In the 

 metaphase of the first division of the fusion nu- 

 cleus, only twelve (12) chromosomes, the haploid 

 number, appear; but later divisions show twenty- 

 four (24), the diploid number. Doubtless, the 

 anaphase would show twenty -four (24), as will be 

 described by Hutchinson in a forthcoming paper 

 on Aiies. 



In the earlier free nuclear divisions there is 

 usually a definite polarity, most of the nuclei be- 

 ing in the upper and lower thirds of the proem- 

 bryo, while the middle third may have no nuclei 

 at all. Toward the close of the free nuclear period 

 all the nuclei in the upper part of the proembryo 

 sometimes divide simultaneously, while those in 

 the lower part remain in the resting condition, so 

 that the nuclei in the upper part become smaller 

 and more numerous than in the lower part. Later, 

 some of the upper nuclei pass to the bottom of 

 the proembryo and, with those already there, di- 

 vide simultaneously, while those above remain in 

 the resting condition. The embryo is formed from 

 these lower nuclei. During the earlier extra-oval 

 stages, haustorial activity is very prominent. 



The Enibryo-sao and Emhryo of Thismia Ameri- 

 cana: Norma E. Ppeiffer. 

 Study of this Chicago representative of the 

 Burmanniacese shows it to differ from some others 

 of the non-chlorophyllous forms in that the mega- 

 spore mother-cell undergoes a reduction division, 



