224 



GENERAL BIOLOGY 



each individual spore-case dries up, that side which is thinnest and has 

 become dried most, splits open, throwing out the spores. There are 

 usually 64 in each sporangium. These spores drop about the moist 

 earth and grow into a minute plant, by first absorbing moisture, and 

 then as the osmotic pressure becomes too great on the inner portion of 

 the spore it breaks, sending out a tiny tube (Fig. 122). This process is 

 called germination ( ). Then a smaller tube ap- 



pears close to the spore body, but from the tiny tube, mentioned above, 



B 



D 



Fig. 120. The Ferns and Their Allies. 



A. Fern plant (Aspidium), showing roots, rhizome, and frond: A., section 

 of fruit dot (sorus), showing spore cases, some of which are ejecting their spores; 

 B., portion of a leaflet, showing unripe fruit dots ; C., portion of a leaflet, showing 

 ripe fruit dots. (After Strasburger. ) 



B. Order I. Salviniales (Floating Allies of ferns). Salvinia natans. 



C. Order II. Equisetales. Branched Equisetum. Equisetum Funstoni, com- 

 monly called "Scouring Rushes," as distinguished from the "Horsetails" (also 

 called Equisetales). The stems of Horsetails die each year and the fruiting cones 

 have no terminal point. 



D. Field Horsetail, showing buds and tubers. 



E. Order III. Lycopodiales (Club-mosses). Common Club-moss, Lycopodium 

 clavatum. 



F. Order IV. Isoetales (Quillworts). Braun's Quill wort, Isoetes echinospora 

 Braunii. 



(A, after Stra^burger : B to F, from W. C. Clute's "The Fern Allies," by 

 permission of The Frederick A. Stokes Co.) 



