April, 1907.] Development of Sporangium of Equisetum. 125 



This is apparently all that has been published on the spor- 

 angia of the group up to the present time and' it seemed that 

 some of the other members should be studied in order to com- 

 pare them with E. limosum and E. arvense as interpreted by- 

 Bower. E. hyemale L. was selected for examination and the 

 sporangium studied, special attention being given to the younger 

 stages. 



The writer's thanks are due to Dr. R. B. Wylie, under whose 

 direction this work was begun, and to Professor John H. Schaff- 

 ner who supervised its completion, for their inany helpful sugges- 

 tions and valued assistance. 



Investigation. 



The material was gathered May, 1905 and 1906, near Sioux 

 City, Iowa, along the north bank of a ravine in rather exposed 

 places and on the north slope of a railroad grade. The killing' 

 solution used was a modification of Fleming's formula and was 

 prepared as follows: 



Chromic acid 15 grams. 



Acetic acid 35 cubic centimeters 



Water 99 . cubic centimeters 



The siliceous protective leaves were reinoved before the 

 young strobili were killed, they were run up through the alcohols 

 in the usual manner and imbedded in paraffin with a melting 

 point of 60 degrees C. The strobili were sectioned longitudinally, 

 sections being cut seven mic. thick. The younger stages were 

 stained in Delafield's haemotoxylin, the older in sanfranin gen- 

 tian violet orange G. combination. 



The young strobilus grows by means of an apical cell, cutting 

 off alternate segments and these dividing both periclinally and 

 anticlinally rather rapidly. No definite epidermal layer is dif- 

 ferentiated. About the time the apical cell has advanced 

 twelve or fourteen segments beyond a certain point and the 

 outer cells have didvied once or twice periclinally the papilla 

 which is the young sporangiophore is noticeable. The first 

 stages of this process are brought about by divisions in the 

 hypodermal tissue and the outer layer does not seem to divide 

 until there is a distinct protuberance. About this stage there is 

 noticeable near the base of this papilla a cell (Fig. 10) with a 

 large vesicular nucleus. It is somewhat larger than its fellows 

 and its cytoplasm gives a peculiar reaction to the stain. It 

 seems to agree rather closely with the initial figured by Bower 

 for E. arvense and was thought to be homologous with it. It 

 divides by a periclinal division forming an upper and a lower cell 

 but in subsequent development only the upper cell functions in 

 the formation of sporogenous tissue the lower one being sterile. 

 In this paper therefore the upper and outer cell resulting from 



