No. 460.] STUDIES ON PLANT CELL. V. 22J 



protoplasm outside of the cell walls, but connected with the 

 cytoplasm within through fibrillae. The intercellular proto- 

 plasm is thus conceived in organic connection with nucleated 

 cells and from the studies of Townsend ('97) we know that non- 

 nucleated protoplasm may live so long as it is united with 

 nucleated, even though it be by very delicate fibrillae. Michnie- 

 wicz (: 04) confirms Kny's conclusions for Lupinus and gives a 

 very clear account of the fibrillae which connect the masses of 

 intercellular protoplasm with neighboring protoplasts. These 

 studies make clearer a number of observations of several inves- 

 tigators (Sauvageau, Buscalioni, Schenk, Magnin, Strasburger, 

 and others) who have noted similar conditions in the tissues 

 of higher plants which are being investigated in detail by Kny. 

 Some of the lower unicellular forms likewise exhibit an extra- 

 cellular surrounding film or envelope, which may also be of a 

 protoplasmic nature and consequently in the same position in 

 relation to the protoplast as intercellular protoplasm. Thus it 

 has been known for many years that the cells of the Peridinales, 

 diatoms, and desmids possessed extracellular material, which 

 some authors have considered in the nature of slimy excretions 

 but others Schutt ('99 ; : ooa ; : oob), Hauptfleisch ('88 ; '95), 

 Muller ('98-'99) have regarded as protoplasmic in character. 

 Since the cell walls in these forms are known to possess pores, 

 such extracellular substance must be in close association with 

 the cytoplasm of the cell and it is not at all difficult to conceive 

 of it as a part of the protoplasm. Some of the peculiar creep- 

 ing movements of the diatoms and desmids are perhaps expli- 

 cable upon these facts. 



2. Sexual Cell Unions and Nuclear Fusions. 



The test of a sexual act must lie with the history of the ele- 

 ments which fuse. If these are shown by their morphology and 

 developmental history to be sexual cells or gametes then their 

 fusion becomes a sexual process. There are cell and even 

 nuclear fusions which have the physiological appearances of 

 sexual acts but cannot be so considered because the elements 

 concerned have plainly no relation to sexual cells, which are 



