THE HIGHER CRYPTOGAMIA. 351 



tion is still in progress. In my experiments the first 

 leaves broke ont from the ends of the prothallia at the end 

 of September, six weeks after the spores were sown. From 

 that time leaves continued to make their appearance singly 

 until the middle of January, when their number suddenly 

 diminished in a remarkable maimer. From the beginning 

 of February until towards the end of March no new germ- 

 plants became visible; at the commencement of spring- 

 however they began to appear again, becoming continually 

 more numerous until the middle of April. Even in the 

 middle of May almost all the prothallia which I examined 

 contained embryos in different stages of development. These 

 prothallia were surrounded by the episporium, and had 

 been produced from a sowing made in the middle of the 

 preceding: August. Such was the result of chamber culture. 

 It is probable that in the natural condition the embryos 

 which break through the prothalliuin in winter do not 

 survive, and that those germ-plants only which are produced 

 in spring attain to a further development. 



Soon after the appearance of the first leaf, the first root 

 also breaks through the prothallium. It bends itself down- 

 wards and penetrates into the mud, the leaf having a vertical 

 direction, inasmuch as being specifically the lighter portion 

 of the plant it stands erect in the water. The prothallium 

 is now attached laterally to the embryo. The thin mass of 

 cellular tissue at its apex forms a ring round that portion 

 of the germ-plant between the root and the front surface of 

 the leaf. The large-celled blunt end of the primary axis of 

 the young plant extends into the principal portion of the 

 prothallium, whose cell- contents, like those of the cells of 

 the first axis of the plant, henceforth become gradually 

 transformed into a transparent fluid. 



After the breaking through of the leaf and the root, the 

 further development of the germ-plant ceases for about a 

 month. Expansion and multiplication of the cells of the 

 first leaf and of the first root still continue, taking place in 

 the former by intercalary multiplication of the cells of the 

 base of the leaf, in the latter by the growth of the apex. 

 But the formation of new leaves and new roots goes on only 

 slowly and gradually. 



