ON THE HOMOLOGIES OF THE SUSPENSOR. 63 



ri'glit angles to the first. Of the four segments thus formed (fig. 

 4), Hansteiu regards the anterior superior as giving rise to the 

 first leaf, the anterior inferior to the apical cell of the stem and to 

 a part of the foot, the posterior superior to the root, the posterior 

 inferior to the larger part of the foot. He points out that the 

 apparent origin of the stem and of part of the foot from the 

 same segment is contrary to expectation. It seems, however, 

 to be unnecessary to regard any portion of the segment from 

 which the apical cell of the stem is derived as forming part of 

 the foot. The apical cell is certainly the one by the divisions 

 of which the stem of the plant is formed, but tlie cells belonging 

 to the same segment are as much representatives of the stem, 

 in the early stages of development, as is the apical cell. Hanstein 

 himself suggests that this portion of the anterior inferior seg- 

 ment should be regarded as a " paracotyledonary " portion of 

 the axis. 



In Salvinia (fig. 5), according to Pringsheim,^ the oosphere 

 is divided by a nearly vertical wall, and the anterior of the 

 two cells formed is divided by a septum at right angles 

 to the first. The superior half of the anterior cell forms the 

 first leaf (cotyledon), and the inferior half the stem. The whole 

 of the posterior cell forms the foot (stielchen — caulicle). The 

 process of development resembles that of Marsilia, but difi'ers 

 in that the posterior of the two primary cells is not dift'erentiated 

 into a root- segment and a foot-segment. In consequence of 

 this Salvinia is entirely destitute of roots. 



It appears that in Ferns the plane of the first division of the 

 oosphere intersects the vertical at a variable angle, but that this 

 angle is always less than a right angle. The division of the 

 two cells thus formed varies in different individuals. Hofmeis- 

 ter- points out that in Pteris aquilina the septum dividing the 

 anterior of the two first formed cells is inclined to the first 

 septum at an acute angle, whereas in Aspidmm filix-mas the 

 angle between the new septum and the first one is nearly a right 

 angle. The septum dividing the posterior cell, in Pteris, is 

 inclined at nearly a right angle to the primary septum, in 

 Aspidium the angle between the corresponding septa is acute. 

 In his account of the development of the embryo of Ceratopteris 

 thalictroides, Kny^ makes no exact estimate of the angles be- 

 tween the primary and the two secondary septa, but it appears 



' " Zur Morplioiogie der Salvinia natans," Jalirbiicli. f. wiss. Bot., iii, 

 1863. 



^ 'On the Higher Cryptogamia,' Ray Society, p. 200. 



^ " Keimung und Eiitwiclcelungsgeschiciitc von Ceratopteris," ' Bnt. 

 Zeitg.,' 1874'. Also, "Die Entwickeluiig de Parkeriaceeii," 'Nov. Act. 

 Leop. Carol. Akad.,' 1875. 



