GENERAL MORPHOLOGY 



297 



the sporophylls no longer servers assimilating leaves, but appear as chaffy 



scales, performing a protective function. It would be difficult to read from 



the comparative study of the mature 



sporophyte in the genus Lycopodium 



any other evolutionary story than this. 

 The only other living genus of 



eligulate Lycopods is the monotypic 



Phylloglossutit) long recognised as the 



simplest of them all. The mature plant 



as seen above ground consists of a tuft 



of almost cylindrical assimilating leaves, 



from the midst of which rises the 



simple axis terminated by the short 



strobilus ; below ground are found two 



ovate storage tubers, one dating from 



the preceding year and in course of 



exhaustion, the other in course of 



development as a store for the succeed- 

 ing year. There are also one or more 



roots (Fig. 145). The lower parts of 



this curious little plant cannot be 



properly understood till it is compared 



with the embryos of certain species of 



Lycopodium, for it repeats in its annual 



growths their embryonic characters : the 



discussion of them will therefore be 



postponed (p. 351). The very short strobilus shows a similarity to the 



Urostachya rather than to the Rhopalostachya section of the genus : this is 

 seen in the smooth margin of the rather fleshy 

 sporophylls, as well as in the incomplete protection 

 of the sporangia. It is interesting to note that tran- 

 sitions are occasionally found between the foliage 

 leaves (protophylls) and the sporophylls : Fig. 



\S I/ .^** 146 A shows a case where a single sporophyll of 



larger size than the normal, with a sporangium 

 in its axil, stands isolated some way below the 

 strobilus : thus it is intermediate both in position 

 and in character between the two types. A small 

 protophyll without any sporangium may also 

 sometimes be found at the base of the pedicel. 

 Dichotomous branching of the strobilus is some- 

 times seen, but it is rare : an example is shown 

 in Fig. 146 B. Such features are important for 

 comparison with Lycopodium, and indicate that 

 there is a close relation between the two genera. 



+ 15 



FIG. 145. 



Phylloglossum Drummondir, Kunze. A = 

 apex of a germinated tuber ; b-, 6-2, b%, leaves ; sp 

 = the young strobilus. X 15. j5=the whole 

 plant. X one^-half. /j = the old tuber; t% = 

 the young tuber; r=root. C sporophyll with 

 sporangium seen from above. X 12. (After 

 Engler and Prantl.) 



FIG. 146. 



Phylloglossum Drummondii 

 Kunze. A = a plant showing pro 



tophylls and strobilus : one sporo- 

 phyll of the latter is at a distance 

 below the rest, intercalary growth 



having taken place in the axis 

 above it. X3. B = a. plant with 

 the strobilus branched into two 

 unequal parts. X 3. 



