174 The Ottawa Naturalist. [Jan. 



spore-cases in their axils, but simply serving as a nutritive basis 

 for the sporophyte tract above them. This is the point where 

 development has ceased in L. selago and L. lucidulum; the 

 lowest leaves of the shoot are purely vegetative, the upper are 

 both vegetative and sporangia-bearing, and next season the 

 growth of the main axis goes on uninterruptedly above this 

 year's apex into another similar tract, vegetative below and 

 fertile above. This is the first step in the formation of a cone; 

 two points are to be noticed: the sporophylls are unmodified, 

 performing a purely vegetative function; and the main axis 

 grows on above the fertile area. The second step was made when 

 the Club Moss put out lateral branches as well as lateral roots, 

 i.e., when the runner was developed. This is seen in L. inun- 

 datum, where the sporangia are limited to a compact terminal 

 spike, the sporophylls are still vegetative and hardly modified, 

 but being appressed and directed upwards they serve to clamp 

 down the sporangia to the main axis and partly protect them; 

 two points are to be noticed: there is no growth possible above 

 the fruiting spike ; and the leaves of the spike are still vegetative. 



The third step was made when a more or less compound 

 system of lateral branches was introduced, and it consists in a 

 further separation of fertile from vegetative tracts by the leaves 

 of the terminal spike ceasing to be assimilative and becoming 

 scales closely imbricated to protect the sporangia within their 

 folds. In L. annotinum and L. obscurum these terminal cones 

 or strobiles are sessile immediately on the apex of the leafy 

 vegetative tract ; in both the cones are single, in the former on 

 primary branches as well as secondary, in the latter on branchlets 

 only. 



The last step, seen in L. clavatum and L. complanatum, is 

 further to separate the reproductive from the vegetative, by 

 raising the scaly cone on a naked or nearly naked peduncle; in 

 L. clavatum this is usually compound, branching near the top into 

 short pedicels, each surmounted by a cone; the branching of the 

 peduncle is usually somewhat one-sided or alternate, and the 

 stronger pedicel is frequently re-divided, so that 3 cones at 

 different distances appear on the peduncle; in L. complanatum 

 it is always compound and more symmetrical, by terminal 

 dichotomy of the peduncle, so that a level-topped cluster of 

 cones is the result, often 4 in number by dichotomy of the 

 pedicels. 



That this story of the development of the Club Moss from 

 the simple to the complex is not a mere figment of the imagina- 

 tion is shown by various species "throwing back"; instances of 

 this sort of atavism or reversion are not infrequent: evidence 

 of the terminal strobile having evolved from an earlier form of^ 



