THE PI.ANT WORLD 79 



Monocotyledons or Dicotyledons. 



By J. Arthur Harris. 



Every one who has begun his botanical work as an amateur, collecting 

 and identifying the plants of his local flora, has found specimens which 

 at first did not fall clearly into either of the great classes, Monocotyle- 

 dons or Dicotyledons. But the name of the genus and the family to 

 which the plant belongs was located in the manual, either from a refer- 

 ence to the common name in the index or after various sections in the 

 key had been tried, and there the difficulty ended. The name of the 

 plant was to be found in Ranunculaceae, Berberidaceae, Nympheaceae, 

 Umbelliferae or Liliaceae, and so the position of the plant was fixed be- 

 yond doubt and no further thought was given to the matter. But if the 

 confidence in the manual is once shaken and the material is more carefully 

 studied the difficulty is not materially lessened. The venation of the 

 leaf, the arrangement of the bundles in the stem or the structure of the 

 flower may place it in one of the classes, but the disposition thus sug- 

 gested is not always supported by the evidence offered by the other parts 

 of the plant, and an attempt to solve the problem by the method best 

 fitted to yield the final and correct decision — the examination of the 

 development, structure and behavior of the embryo itself — has shown 

 that the difficulty experienced in referring certain plants to one or the 

 other of two great classes is not one of similarity of external appear- 

 ance alone but of fundamental structure as well, and presents a most 

 interesting problem for solution. 



Excellent illustrations of the point just stated are the lotus (^Neluni- 

 bi7int), of the Nympheaceae, and the may-apple iPodophyllurri), and two 

 other interesting forms, Diphylleia and Jeffersonia, referred to the Ber- 

 beridaceae, while other forms equally interesting and puzzling might be 

 mentioned . While on the most of these forms the careful developmental 

 work which alone can yield a final and satisfactory solution has not yet 

 been done, it is of the greatest interest to know that investigations upon 

 the embryogeny of Nelumbium have shown that its position among 

 Dicotyledons is by no means an unquestionable one, but that it seems to 

 belong quite clearly to the Monocotyledons. The work upon the devel- 

 opment of the embryo has shown that primarily there is a single coty- 

 ledon which becomes divided, giving rise to the two "cotyledons" 

 which have till recently determined its position in the Dicotyledons, for 

 the structure of the vegetative parts are by no means characteristically 

 dicotyledonous, nor on the other hand are they typically monocotyledo- 

 nous. In Podophyllum, both our common may-apple and the closely 



