March 21, 19(l2 ] 



SCIENCE. 



457 



The oogonia when cut oif contain about 

 fifty nuclei, which move toward the periph- 

 eiy while the interioi- is still a coarse 

 cytoplasmic mesh-work. Patches of fine 

 meshed cytoplasm now arise at various 

 places in the oogoniiun; these later fuse 

 into one central irregular mass which never 

 loses its mesh-like character. This central 

 structure, which corresponds to bodies pre- 

 viously observed in the Peronosporinese and 

 Pythium, reaches its highest development 

 at the time the sperm nucleus enters. Soon 

 afterwards it begins to spread out into the 

 peripheral ooplasm. Just before the sepa- 

 ration of egg from periplasm, the nuclei 

 probably all divide once, mitotically. The 

 egg, when ripe, consists of this previously 

 described central area, which now has a 

 female nucleus imbedded in it, surrounded 

 by a coarse, uniformly vacuolate peripheral 

 portion. Enclosing the egg, though sharp- 

 ly marked off from it, is the periplasm 

 which, at this time, is divided anticlinally 

 into a single layer of cells. 



No such structure as an antheridial tube 

 was seen. The fertilizing tube is entirely 

 of oogonial origin. The protoplasm in 

 contact with the oogonial wall where the 

 antlieridium is appressed, and where the 

 oogonial papilla is developed, always 

 remains with the ooplasm. Consequently, 

 the plasma membrane of the periplasm, as 

 it lays down a wall between it and the 

 ooplasm, builds the wall of the fertilizing 

 tube. As soon as this tube is formed, the 

 perforation is made by the papilla and a 

 sperm nucleus and some cytoplasm are 

 admitted. As the nuclei approach, both 

 put out beaks which, at least in some cases, 

 fuse. When the wall of the oospore is 

 well developed the latter is binucleate. 

 The important points in the paper are : 

 [a) Fertilization takes place by the union 

 of a single male and female nucleus. (6) 

 An organ of attraction for the sexual nu- 

 clei arises in the early development of the 



oogonium and its origin, structure and fate 

 is followed, (e) There is no such fertili- 

 zation tube as is figured in related forms. 

 The tube here is a conjugation tube and 

 the opening a conjugation pore, as Harper 

 lias suggested in Pyronema. Illustrated by 

 lantern slides. 



Frederick DeForest Heald : ' The Elec- 

 trical Conductivity of Plant Juices.' Us- 

 ing the methods of physical chemistry, con- 

 ductivity measurements were made for the 

 juice expressed from the leaves, stems, 

 roots, etc., of diif erent plants. The follow- 

 ing species were used: Beta vulgaris, So- 

 laniim tuberosum, Allium cepa, Raphanus 

 sativus, Nupliar advena, Cucumis sativus, 

 Amarantiis retroflexus and Portulaca olera- 

 cea. Ash determinations were also made 

 for the juices used and the ash redissolved 

 in distilled water and diluted up to the 

 original volume of the juice from which it 

 was obtained. Specific conductivity deter- 

 minations were made for the ash solutions. 

 The following conclusions were drawn from 

 the various determinations, (a) Plant 

 juices are comparatively good conductors, 

 the conductivity being due in large meas- 

 ure to the dissolved mineral substances, 

 while the organic compounds play a minor 

 part. (6) The specific conductivity of the 

 juice obtained from the roots of plants is 

 always considerably less than that of the 

 juice obtained from the subaerial parts of 

 the plant, (c) The specific conductivity 

 generally increases progressively from the 

 root upward, although in some cases the 

 sap from the stem has a higher conductiv- 

 ity than that from the leaves, (d) In the 

 majority of cases the specific conductivity 

 is a rough measure of the relative amount 

 of ash present in different parts of the 

 plant. Illustrated by lantern slides. 



H. G. TiMBERLAKE : ' Starch Formation 

 in Cladophora.' The process of starch for- 

 mation in Cladophora was described as oc- 



