Butters: seeds and seedling of caulophyllum. 21 



After tlie cotyledons appear they grow much faster than the body 

 of the embryo, so that about ten days after the first appearance of 

 their primordia the cotyledons equal the hypocotyl in length, the 

 embryo exclusive of the suspensor measuring about i mm. in 

 length. 



Later, the growth is much slower, the embryo reaching the length 

 of 1.5 mm.- 1.7 mm. during the succeeding month, and 2 mm.-2.25 

 mm. in the ripe seeds collected in autumn. Of this length about three- 

 fifths is occupied by the cotyledons (Fig. 15-17, PI. V). 



There is no tendency to develop a cotyledonary tube during the 

 maturing of the embryo as is the case in Podophyllum and some 

 other related plants, but the cotyledons remain separate, the sinus 

 on each side extending to their base (Fig. 16, PI. V). The growth 

 of the cotyledons is accomplished by cell division occurring through- 

 out their tissue. At first they increase somewhat in thickness as 

 well as in length in their proximal portion, but not at the extreme 

 base, nor in the distal half. The latter part grows considerably in 

 width. The result is that the cotyledons become somewhat spoon- 

 shaped with the concave faces toward each other. They are con- 

 tracted at the base, while immediately above this they approach 

 each other, almost enclosing a small conical space above the apical 

 portion of the axis of the embryo (Fig. 15, PI. V). This apical 

 growing region of the epicotyl at first projects little above the plane 

 of the bases of the cotyledons, but it gradually develops, and in 

 the mature seed forms an epicotyledonary mound of tissue about 

 80 mic. high, which nearly fills the conical space between the bases of 

 the cotyledons. As the embryo grows it disorganizes the surround- 



and wax models were reconstructed from the sections in the case of several 

 embryos, series both of longitudinal and of transverse sections being thus era- 

 ployed. In reconstructing embryos of Caulophi/Uum the remarkably symmetri- 

 cal shape of the part of the seed in which the embryo is located is of great 

 aid in determining in what degree the sections are oblique to the axis of the 

 seed. This angle was carefully calculated for each series of sections pre- 

 vious to reconstruction. Although in several series sections occurred almost 

 exactly like those figured by Mr. Lewis, their peculiar shape proved to be due 

 to oblique sectioning of the embryo, and not to the crescentie primordium which 

 Lewis postulates. 



Subsequent to the reconstruction of the embryos shown in Plate X, a num- 

 ber of embrj'os were dissected out of seeds and examined directly under a 

 Zeiss binocular dissecting microscope. They were found to have almost ex- 

 actly the form which had been obtained by reconstruction and which is 

 shown in Plate X. There is in fact, less, rather than more, deviation from 

 perfect symmetry than is shown by the models. 



