294 Kansas Academy of Science. 



Class IV. EQDISETINEAE: Joint Hushes. 



Erect, hollow, jointed and banded sporophy tes, having a fluted or clustered- 

 columnar structure, with solid nodes and whorled rudimentary leaves, arising 

 from perennial, horizontal, hypogean stems or * ' rootstocks. ' ' The sporangia 

 (spore-pockets) on the under side of the sporophyls, in a cone at the summit 

 of a sporophore, develop from a cluster of epidermal and subepidermal cells 

 (eusporangiate), and the spores are all of one size (microspores), each fur- 

 nished with two strap-like hygroscopic appendages, attached by the middle, 

 that coil close around the spore when moist, and uncoil when dry. In this 

 class of plants the cone is adopted as a method of fructification, a system 

 that reaches its greatest perfection in the Coniferae, but is considerably 

 modified in other classes. 



Order IX. EQUISETALES: The Horsetails. 



( Homosporous Eusporangiate Arthrocaulones.) 



Sporophytes semiaquatic or terrestrial, herbaceous, with uniform spores 

 which develop into irregularly-lobed green prothallia (oophytes) on 

 the surface of the ground. These prothallia are dioecious ; some 

 bear fertile antheridia, carrying spiral multiciliate antherozoids, 

 somewhat like those of the quillworts ; others bear flask-shaped 

 archegonia, each with a single ovum or oosphere at the bottom. 

 From a union of the antherozoids with the ova, or oospheres, brought 

 about through the agency of wind, moisture, rain, and other natural 

 factors, new horsetail plants are produced. 



Stems of two kinds: (a) A compound vegetative stem, normally well 

 supplied with branches and branchlets, all chlorophyl-developing; 

 and (6) a stout, simple, fertile stem that bears on its summit the 

 sporangiophore, which consists of a closely-packed conical or spike- 

 like cluster of stalked or pediceled peltate hexagonal or shield- 

 shaped sporophyls, called clypeolas. Spore-bearing pockets 

 (sporangia), 6 to 9, under the edge of each clypeola, one-celled, 

 dehiscing by a longitudinal slit beneath. Leaves rudimentary, 

 verticillate, at the summit of each joint, as many as the flutings, 

 which alternate with the flutings in the joints above and below, 

 and consisting of mere toothed sheaths having their edges joined 

 together, thus making a leaf band at each node. This suggests 

 the name Equisetum—Equi, equal, and setum, a bristle. The teeth 

 are equal. Epidermis rough with silica. Stems and branches all 

 chlorophyl-developing, making the possession of large leaves un- 

 necessary. 



Family 24. Equisetace.e : Horsetail Family. 



159. Equisetum arvense L. Field horsetail. Sandy soil, eastern 



Kansas, west to Barton and Republic counties, and even 

 farther; common. (A S U) 



160. Equisetum pratense Ehrh. Meadow horsetail. Sandy mead- 



ows, E. K. ; frequent. 



161. Equisetum fluviatile L. River horsetail. Banks of streams, 



E. K., west to Ford county; frequent. (A S U) 



162. Equisetum robustum A. Braun. Big scouring-rush. Barton 



county; not common. (S U) 



