SELAGINELL^E. 



385 



Four genera belong to this order, viz., Lycopodium, which is common 

 in the wooded portions of the United States ; Puilotum, found in 

 Florida ; Tmesipteris and Phylloglosaum, of Australia. The species 

 number from 115 to 120, of which about 100 belong to the genus 

 Lycopodium. 



The spores of Lycopodium clavatum are gathered in Europe and 

 sold for various minor uses. Many species have a high ornamental 

 value. 



This order was represented in the Devonian by species of Arctopo- 

 dium. In the Carboniferous the genus Lycopodium first appeared. 



The closely related extinct order Lepidodendreae first appeared in the 

 Devonian, in which it was represented by two known species of Lepi- 

 dodendron ; in the Carbonif erous this genus was represented by sixty or 

 more species, many of gi- 

 gantic size, and the order 

 by many other genera e.g., 

 Lepidophloios, Lepidostro- 

 bus, HaUmia, etc. In the 

 Permian this order became 

 extinct. 



Another order the Sigil- 

 lariese was represented by 

 many species of Sigillaria 



in the Carboniferous period. 



,. r, . Fig- "77. /., two young plants of Sdagimlla 



Like the preceding, this or- Marteitsii growing from the same spore ; at the 

 top of the spore may be seen the projecting pro- 

 thallium, p. II., a young plant drawn out of the 



, . ., 



spore, showing the foot, /, on the left below, and 

 the young root, r, on the rijjlit. ///., a young 



der became extinct in the 

 Permian. 



Order Selaginellee. plan j Wn o 8e flrst leaves (cotyledons) have been r? 



The prothallia are dioecious, moved, leaving only their stipules, s; between the 



T1ir>s whipli (Wplnn from latter is seen tne dichotomously dividing -punctum 



lliose wlucli develop Irom veffeta tionts ; p, the prothallium isolated from the 



the inacrospores consist of a spore. /. x 5 ; //. x 3 ; ///. x 30. After Hof- 



,. , meister. 

 concavo-convex many-celled. 



structure, which develops upon, and has its concave side applied to, the 

 convex surface of the spore. Upon its convex surface, which protrudes 

 through the ruptured wall of the spore, are a few root-hairs and many 

 deeply sunken archegonia (Fig. 276, 1, 2, 3). The microspores develop 

 only the smallest rudiments of prothallia. In germination a single 

 cell (v, Fig. 276, D) is first of all cut off ; this undergoes no further 

 change, and is doubtless to be regarded as the prothallium. The re- 

 mainder of the spore becomes divided in a regular way into a few 

 large primordial cells (Fig. 276, ^.41, and from these great numbers of 

 sperm-cells are produced (Fig. 276, D). 



After fertilization the germ-cell divides at right angles to the axia 

 of the archegonium (Fig. 276, 3) ; from the upper cell so formed a 

 tuspensor is developed (Fig. 276, 1), while the lower develops into the 

 embryo. The embryo, by its rapid growth, comes eventually to occupy 



