April, 1907.] Development of Sporangium of Equisetum. 
12 3 
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 many 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 removed 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 
