2t8 the AMERICAN naturalist, [Vol. XXXIX. 



offers at once many interesting possibilities of explaining the 

 close association of many cells and tissues, not alone in delicate 

 dynamic interrelations but even in the exchange and distribution 

 of food material and other products of meta;bolism. It makes 

 possible the conception of the plant body as a finely adjusted 

 community of protoplasts intimately and sensitively related to a 

 great 'degree in all parts, a view very different from the old idea 

 of a cell republic. As might be expected, these speculative 

 possibilities were conceived and expressed by such leaders as 

 Hofmeister, Nageli, Sachs, and Strasburger long before the 

 detailed study of protoplasmic connections gave the mass of evi- 

 dence upon which have been based the more elaborate concep- 

 tions of recent years. 



The most obvious protoplasmic connections between cells may 

 be found in the thallophytes where as in the Rhodophyceje, 

 Volvox, and in certain fungi, the cells in younger structures may 

 be observed under comparatively low magnification to be united 

 by strands of protoplasm so broad as to quite exclude them from 

 the category of fibrillse. Some of these structures are so con- 

 spicuous that it is surprising that more was not made of them by 

 early writers and that they have not been more extensively 

 investigated recently. The greater part of the papers have 

 been on the very difficult phase of the subject, the structure of 

 pores and pits in the tissues of higher plants. The literature 

 treating of protoplasmic connections is too extensive to be given 

 detailed treatment in the compass of this paper. The best 

 review of the subject is that of Strasburger (: oi), supplemented 

 by the more recent paper of Kienitz-Gerloff (:o2). 



The earlier papers on the protoplasmic connections in higher 

 plants, following the establishment of perforations of sieve-plates 

 by Sachs and Hanstein, appeared during the years just preceding 

 and following 1880. Thus Tangl ('79-'8i) described very clearly 

 the communications between the endosperm cells of Sfrvc/nios 

 Hitx vomica and Phoenix (see Fig. 16, a). Tangl noted the resem- 

 blance of the complex of connecting threads to the arrangement 

 of spindle fibers associated with the simultaneous division of the 

 protoplasm m the endosperm but was cautious in assuming a 

 relationship, suggesting that the resemblance might be super- 

 ficial. 



