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THE AMERICAN NATURALIST. [Vol. XXXVIII. 



cate peculiarities of structure and a degree of permanence as 

 cell organs that is not actually present. It seems hardly neces- 

 sary to define the plasma membranes further than by their posi- 

 tion in the cell as the outer, vacuolar and nuclear membranes. 



All of the cytoplasm bounded by the plasma membranes with 

 the exception of certain conditions to be described later (centro- 

 spheres, centrosomes, asters, filarplasm and blepharoplasts) may 

 be called trophoplasm since it contains structures and substances 

 especially concerned with nutritive functions. Trophoplasm 

 presents an open organization in sharp contrast to the dense 

 kinoplasm. This peculiarity is due in part to numerous small 

 vacuoles which give a spongy appearance to the usual foam like 

 structure and is further complicated by the inclusion of material 

 not strictly a part of the protoplasm in the form of various sized 

 granules. There are sometimes present fibrillse that impart a 

 somewhat fibrous texture. We cannot discuss here the theories 

 of the structure of protoplasm, which has not been so extensively 

 studied in plants as among animals, further than to point out 

 that it varies considerably in different regions of the cell in 

 relation to peculiarities that will be described later. There is 

 sometimes presented very typically the foam structure of 

 Butschli but the introduction of small vacuoles generally gives a 

 spongiose appearance. This subject is critically reviewed by 

 Fischer, '99, and has also been treated in several papers of 

 Strasburger especially in '97. 



Three well differentiated organs of the cell, probably tropho- 

 plasmic in character, require special mention, viz., ccenocentra, 

 nematoplasts and physodes. Coenocentra are very interesting 

 protoplasmic centers found in the oogonia of certain coenocytic 

 fungi among the Saprolegniales and Peronosporales durmg 

 oogenesis. They appear just previous to the differentiation of 

 the eggs as small bodies sometimes with delicate radiations (see 

 Fig. 3, a and 8,/), and are found one in each egg origin. They 

 are apt to increase in size as the eggs mature and evidently 

 become the centers of the metabolic activities of the cells, 

 drawing the sexual nuclei into their neighborhood where the 

 latter increase in size (Fig. 3, a 2). The coenocentrum dis- 

 appears in the ripe oospore and is consequently an evanescent 



