24 minnesota botanical studies. 



Germination of the Seed. 



The seeds of Caulophyllum germinate very slowly. Seeds were 

 collected and planted in the autumn, before the pulp had dried, and 

 others were planted in the spring after lying under the snow for 

 one winter. None of them showed any external signs of germina- 

 tion in the following December — fifteen months after their maturity. 

 An examination of the embryo of these seeds (Fig. i8, PI. V) 

 showed, however, that it had increased considerably in size. The 

 cotyledons, especially, were found to have elongated to over twice 

 their former length, and to have increased by one-half in width, 

 and they had pushed their distal ends well up into the body of the 

 seed. Although the hypocotyl had increased somewhat in length, 

 changes in that region were far less marked than in the cotyledons. 

 The epicotyl was almost unchanged except for a slight growth most 

 noticeable from the development of definite rows of cells in the 

 interior where the cells were irregularly parenchymatous before. 



After this stage is reached, the germination of the seed progresses 

 rapidly, if the environment is favorable. This occurs usually, under 

 natural conditions, during the early part of the second summer. The 

 radicle projects from the seed, partly as a result of its own growth, 

 partly on account of the rapid elongation of the proximal portion 

 or petioles of the cotyledons. This process continues until the en- 

 tire hypocotyl is pushed out of the seed with which it is connected 

 by the two cotyledonary petioles about 8mm. long. At the same 

 time the spoon-shaped distal portions of the two cotyledons grow 

 rapidly, coalesce, and together form a peculiar haustorial organ 

 which occupies the center of the seed. This haustorium takes the 

 form of a hollow sphere invaginated on one side, thus conforming in 

 a general way to the shape of the seed (Figs. 21 and 22, PI. \T). 

 Its wall is about one-half mm. thick, and its surface is marked with 

 low convolutions. While the line which marks the division between 

 the two cotyledons in this haustorium can be seen on close exami- 

 nation, it is not at all conspicuous, and the union of this portion 

 of the cotyledons appears to be complete. As the petioles of the 

 cotyledons elongate, they form a very short cotyledonary tube 

 (about 100 mic. long) at their base. Otherwise they are entirely 

 separate. They join the haustorium at the middle of its concave side. 

 During the first year's extra-seminal growth of the embryo, the 

 haustorium continually increases in size, until at the close of the 



