Biological Paper's. 293 



Order VIII. ISOETALES : The Quillworts. 



rushes or grass leaves somewhat. The outer cycles of sporophyls 

 bear in their axils or on their inner surfaces solitary gynosporangia, 

 with spheroidal gynospores measuring one-fourth to three-fourths 

 of a millimeter in diameter, with a reticulated surface, an equa- 

 torial ridge and three meridional ridges from the equator to the 

 initial pole, making the entire spore resemble a low tetrahedron 

 attached by its base to the flat side of a reticulated hemisphere. 

 In the inner cycles each sporophyl bears a single androsporangium, 

 carrying minute, obliquely oblong prismoidal androspores, 25 to 40 

 microns in diameter. 

 Gametophytes dioecious; those produced from the androspores are here 

 very much reduced and are very minute, microscopic in fact, and 

 parasitic, each bearing but a single antheridium; the archegonial 

 gametophytes, those produced from the gynospores, after fecunda- 

 tion of the ova, become small globular bodies developing within 

 the sporophyte gynospore wall and not escaping therefrom, the 

 wall being ruptured only to allow access of antherozoids. This is 

 yet another long step toward the development of the seed-bearing 

 plants. Indeed the resemblance of the quillwort to a seed-bearer 

 is very strong; it is frequently mistaken for a grass or a sedge, 

 else it might oftener be recognized as a quillwort. This euspo- 

 rangiate-heteroaporous combination is the one that pervades the 

 entire carpellate subkingdom. It has proven effective in plants 

 that breed in air, even more so than those that breed in water, 

 and is never afterward wholly abandoned. 

 There is but the one genus, Isoetes, in this anomalous order of Isoetales, 

 placed here for convenience without any claim that it belongs here 

 more than elsewhere. The real truth is, it has fern and horsetail 

 characteristics in its spiral multiciliate antherozoids, horsetail 

 characteristics in the verticillate arrangement of its leaves, and 

 club-moss characteristics in its solitary sporangia and the form of 

 its gynospores. It differs from the stereocaulones in the form of 

 its leaves and in its mode of fruit-bearing; from the arthrocaulones 

 in being stemless and in its mode of spore-bearing; and differs from 

 the lepidocaulones in having verticillate leaves and in its sperms 

 being multiciliate instead of biciliate. 



Family 23. Isoetace^: Quillwort Family, 



157. Isoetes butleri Engelmann. Butler's quillwort. Cherokee 



county (Hitchcock). (A) 



158. Isoetes melanopoda J. Gay. Black-based quillwort. Greeley 



county, in a shallow, clay-bottomed, water-holding, often 

 dry basin west of Horace; rarely seen and recognized. 

 Sept. (S) 



Subphylum B. ARTHROCAULONES (Equisetse). 

 Joint-stemmed Pteridophytes. 

 Archegoniate plants in which the sporophytes have tubular or hollow 

 stems, with articulations or joints at intervals along the stem. There is 

 only one class. 



