588 THE AMERICAN NATURALIST [Vol. XLII 



at the base of the suspensor (PI. II, Fig. 20). The walls 

 of the cells composing the innermost layer of the seed 

 coats become somewhat thickened and rounded. Later 

 the cells increase greatly in size and become very stony 

 in texture. All the other layers except the external one, 

 which forms a delicate membrane, disappear. 



By some botanists Myosurus has been considered a 

 low type from which the monocotyledons and dicotyle- 

 dons took their origin. This view was based principally 

 upon its external vegetative structure. If it stands on 

 the border line between these two groups, one would 

 expect to find in its embryology features common to both 

 and perhaps one well-developed cotyledon and another 

 rudimentary one. But this is not the case. The cotyle- 

 dons from their first appearance clear through the period 

 of germination are exactly equal. And, furthermore, the 

 other features of development are typically dicotyle- 

 donous, corresponding to those of the other Banuncu- 

 lacese. It is, however, to be regarded from its embryo- 

 logical and vegetative fatures as one of the lowest, if 

 not the very lowest, of the dicotyledons. 



This work was carried on in the department of botany 

 of the University of Nebraska, under the direction of 

 Dr. Charles E. Bessey, to whom I am indebted for his 

 interest and assistance. 



