228 PTERIDOPHYTA. 



Highlands of Scotland. The other genus of the order is Phylloylosstini, with 

 one species, P. drnmmondi (Australia, Tasmania, and New Zealand), a small 

 plant only a few centimetres high, with two tubers, and about eleven linear 

 leaves at the base of the stem which is terminated by a cone of sporophylls. 

 FOSSIL Lycopodiacefe in the Carboniferous period. 



OFFICINAL: "Lycopodium," the spores of L. dnvatuni. 



Family 2. Psilotaceae. The sporangia are placed on the apex of short, two- 

 leaved stems, as 2-3, seldom four, small capsules. Small herbs, with angular 

 stems ; leaves small, simple, and one nerved. Only four species. Psilotnm 

 (Madagascar, Moluccas, Sandwich Islands, etc.) is destitute of roots, their place 

 being supplied by special underground stems which bear a few modified leaves, 

 very much reduced, especially when buried deeply in the soil. Three species. 

 Tmesipteris (Australia), one species. 



Sub-Class 2. Selaginelleae (HETEROSPOROUS Lycopodinse). 



Micro- and macro-spores. The prothallia are very much reduced, 

 especially the male ; the female does not leave the spore. The 

 leaves are ligulate. 





-- 



A 



B 



Kn;. L'315. Germination of the microspores of Sclaginclla : A the spore rendered 

 transparent, seen from above. In the interior is seen the protballium (/), and the first 

 divisions of the antheridium (<i, f>, c, d) ; in B the spore-wall is removed and all 

 the spermatozoid-mother-cells formed; in C, the microspore has opened and the spermato- 

 zoids and the mother-cells are escaping together. 



The sexual generation. In the MICROSPORES are formed: 

 (1) a very small "vegetative" cell, representing the vegetative 

 part of the prothallium (/ in Fig. 233 A, B), and (2) a cell many 

 times larger and which divides into a number (4-8) of primordial 

 cells, each of which divides into four spermatozoid-mother-cells, 

 1 hough all of these may not develops spermatozoids. On germina- 

 i ion, when the spore- wall is ruptured, the spermatozoids and 

 spermatozoid-mother-cells are ejected into the water. 



The SPERMATOZOIDS in Selagmella are elongated and club-shaped, 

 with two cilia (Fig. 234) ; but in Isoetes lacustrls they are spirally- 

 twisted threads which differ from all other spermatozoids by 



