GENERAL MORPHOLOGY 441 



O. simplex, Ridley. 1 This ground-growing mycorhizal plant has tall fertile 

 spikes, without any sterile lamina. Anatomically as well as in form it 

 resembles O. pendulum but more especially in its external characters and 

 habit it resembles the rare O. intermedium, Hook, which is also a 

 Mind-growing species. For reasons explained at length in the paper 

 >ve quoted, it is thought that O. simplex forms the end of a series of 

 iuction of the vegetative system consequent on a mycorhizal habit and 

 laded habitat : that as O. intermedium, when compared with O. pendulum, 

 shows a relatively large spike but only a reduced lamina, so in O. simplex 

 the reduction having proceeded further has resulted in the complete 

 elimination of the sterile blade. 



In the genus Botrychium the construction of the upright stock is 

 essentially similar to that of . Ophioglossum, and the plants are habitually, 

 though not always monophyllous. The main external difference lies in the 

 branched form both of the sterile leaf and of the fertile spike : these parts 

 show a similar parallelism of ramification to that which is present though 

 less regular in O. palmatnm. According to the complexity of the two 

 parts the species may be arranged, starting from those very small and 

 simple forms included under the name Botrychium simplex. These are 

 held by Luerssen not to be actual varieties, but rather plants of various 

 ages, and therefore in different stages of development which pass into 

 one another, a point which greatly increases their interest (Fig. 240). The 

 sterile leaf in the smallest of these may be entirely unbranched, as in a 

 small Ophioglossum, while the fertile spike is also unbranched, and bears 

 a very small number of sporangia (Figs. 240 A-F) : these appear in the simplest 

 cases as individual lateral projections from the spike, but here, as in the 

 whole genus, they are disposed along its lateral margins, in the same 

 relative position as in Ophioglossum. The steps from this simple condition 

 are clearly shown in Luerssen's drawings (Figs. 240 G-L), lobation of the 

 sterile leaf progressing in marked parallelism with branching of the fertile 

 spike : first a simple pinnation, and then an incipient double pinnation. 

 The condition is thus attained which is seen in the common B. Lunaria 

 (Fig. 241), where the pinnation in its different forms may be single or 

 double. And so onwards through the species, the sterile leaf may be 

 three (B. daucifolium\ or even four times pinnate (B. virginianum), the 

 fertile spike showing a corresponding complexity. The whole genus from 

 the simplest to the most elaborate, shows such gentle gradations of change 

 that the unity of type throughout is unmistakable. 



Various abnormal modifications have been described for Botrychium, 

 some of them involving the formation of accessory parts, such a 

 doubling of the sterile leaf, or increase in number of the fertile spikes, as 

 in Ophioglossum ; but no species of Botrychium is recognised in which this 

 is established as a permanent character. The abnormalities involving dis- 

 tribution of the sporangia are the most important : all stages of vegetative 

 1 See Ann. of Bot., 1904, p. 205. 



