

191 



Plasmodesmen. 



By Frank Marion Andrews. 



It lias been shown by W. Gardiner, 1 Strasburger, 3 Kohl, 2 and others 

 that plasmodesmen are not confined to the pits in the cell walls but that 

 they may also penetrate the cell walls themselves at other places. Excel- 

 lent names for the plasmodesmen penetrating the cell wall in the places 

 above mentioned have been chosen by Kohl. 4 Those which pass through 

 the pit membrane he calls aggregated and these which pass through the 

 unpitted membrane solitary. Strasburger' has recommended for all these 

 protoplasmic connections the term plasmodesmen. It has also been shown 

 that the plasmodesmen arise independently of cell division, for in the 

 dermatogen of a phanerogam, in which only anticlinal and radial walls 

 are formed these plasmodesmen are present in the walls between the der- 

 matogen and the next inner layer of cells. 



The plasmodesmen arise, according to Strasburger. secondarily in a 

 very early stage in the formation of the membranes, before the beginning 

 of their secondary thickening. Pfeffer states — according to reports — that 

 a subsequent formation of very thin plama connections is just as possible, 

 as the larger fusion of protoplasts, which is made possible by dissolution 

 of adequate parts of the cell wall. 



I have investigated the occurrence of plasmodesmen to some extent 

 in the endosperm of Phoenix daetylifera. and find both the solitary and 

 aggregate forms present in large numbers. 



Fig. 1 represents a cross-section of a cell of the endosperm of this 

 plant before treating with any reagent. The pits are large and numerous 

 and are generally somewhat enlarged where the ends come together with 

 the corresponding ones of contiguous cells. The walls are rather thick 

 and hard. Fig. 2 is a longitudinal section of the endosperm of Phoenix 



'Gardiner \V. Arbeiten des Botanischen Institutes in Wurzburg 1888, Bd. 3, p. 52. 

 3 Strasburger Ueber Plasmaverbindungen pflanzlicher Zellen Jahr fiir wis. Bot. 1901, 



Band 36, p. 493. 

 2 Kohl-Ber. d. Deutsch botan. Gesell=ch. 1900, p. 364. 

 4 Kohl-Ber. d. Deutsch botan. Gesellsch. 1900, p. 364. 

 E Strasburger-Ueber Plasmaverbindungen pflanzlicher Zellen Jahr fiir wis. Bot. 1901, 



Band 36, p. 503. 

 °Pfeffer-Pflanzenphysiologie zweite Auf. 1904, Bd. II, p. 219. 



