642 MOSSES AND FERNS 



The difference in size between the two sorts of sporangia is most 

 marked in those where the macrosporangia are confined to the basal 

 portion of the cone. 



P. 529. For a detailed discussion of the morphological nature of 

 the rhizophore see Worsdell (i). 



P. 530. For Goebel (16), read (9); for Bower (15), read (14). 



P. 532. There is considerable variation in the number of mega- 

 spores that may be formed (Mitchell (i) ). While in most cases 

 there are four, the number may be reduced to two, e.g., S. rupestris, or 

 even a single one, e.g., S. sulcata. 



Conversely, cases have been observed where more than one mother 

 cell divides so that the number exceeds four. Miss Mitchell observed 

 twelve in a specimen of S. Vogelii, and eight in one of S. involvens. 

 In S. Helvetica Kainradt (i) found that not infrequently two spore- 

 tetrads were formed, and in one case four complete spore- tetrads 

 were seen in a macrosporangium. 



CHAPTER XIV 



P. 534. For Sadebeck (8), read (9). 



P. 536. See Wernham's paper on Phylloglossum (i), for a compari- 

 son of that genus with Isoetes. 



P« 553- One of the recent accounts of the anatomy of Isoetes is 

 by Miss Stokey (i), who examined four species. Her account agrees 

 essentially with that of other observers. Her conclusion as to the 

 systematic position of Isoetes is that it should be placed in the Lycopo- 

 diales. Lang (14) has still more recently made an elaborate study 

 of the general morphology of the stock of /. lacusiris, 



P. 554. The type of secondary wood in Isoetes has been compared to 

 that of the fossil Lepidodendreae. (See Stokey (i), p. 332.) 



CHAPTER XV 



P. 563. See Allen (i). 



P. 569. The embryo of certain species of Ophioglossum {e.g., O. 

 Moluccanum) probably resembles that of the ancestral Fern. It con- 

 sists at first simply of the large foot and the young primary leaf. At 

 this stage the embryo bears a marked resemblance to the young 

 sporophyte of Anthoceros. The root arises somewhat later, deep 

 down in the tissue near the junction of the leaf and foot. As this 



