906 III. EQUISETACE^. 



sheaths is furnished with stoinata, of which the position is always limited to those 

 parts which cover a parenchyma filled with chlorophyll. The siliceous layer which 

 covers the epidermis is looked upon by M. Duval-Jouve as a secretion from that part 

 of the cells which is in contact with the air, and not as entering into the compo- 

 sition of their membranes, as several authors maintain. 



FRUCTIFICATION in spikes or conical catkins, either aestival and terminal, or 

 vernal and springing directly from the rhizome. SPIKE formed of several whorls of 

 horizontal pedicels, vertically dilated at their free end into a peltate body (clypeola), 

 bearing on its inner face G-9 sporangia, whorled around the pedicel, and parallel to 

 it. SPORANGIA, at the period of the emission of the spores, dehiscing longitudinally 

 on the side facing the pedicel. 



SPORES very numerous, free, uniform, spherical, and bearing two filiform ap- 

 pendages (elaters) dilated at each end into a flattened very hygroscopic and spirally 

 coiled spathula, which uncoils under moisture. Before expansion the elaters 

 form, according to M. Duval-Jouve, a hollow sphere around the spore, their common 

 point of attachment being on the equator, and their spathulate ends on the poles of 

 the spores. The spores germinate as in Ferns, developing an irregularly lobulate 

 dioecious or monoecious prothallus, which bears antheridia at the end of its lobes, and 

 archegonia on the upper surface of the fleshy tissue of its base. 



The ANTHERIDIA appear as ovoid swellings, composed of large cells enveloping a 

 central group of prismatic cells, which soon multiply into a number of cellules, each 

 containing a flattened ellipsoid globule. Soon after, the walls of these cellules dis- 

 appear, and the globules (the future antherozoids) become isolated. After some days 

 there appears within the globules a colourless imperfect ring, with unequally 

 swollen ends, fixed against the circumference of the disk, of which it occupies three- 

 fourths, the remaining space being occupied by a mucilaginous mass. Soon the 

 terminal cells of the antheridia separate at the top, spread out so as to form a 

 crown, and leave a passage for the globules ; these are no .sooner set at liberty than 

 they are seen to quiver, and oscillate like a pendulum. These oscillations continue 

 for a few seconds only, after which the antherozoids are found to have replaced 

 the globules, not the smallest trace of the latter remaining. M. Duval-Jouve, who 

 has published a very beautiful and complete monograph of this family, thinks that 

 the globule is absorbed simultaneously with the formation of the antherozoid. The 

 antherozoids of Equisetacece are formed like those of Ferns, and have the same 

 faculty of translation. 



The ARCHEGONIA are found near the lobed branches of the prothallus ; these 

 branches are nearly always deprived of antheridia at their extremity ; their lower 

 part is thicker, and composed of cells smaller than those of the antheridiferous 

 branches. This fleshy region bears several small bright red cellular cushion-like 

 organs, with a globose base (ventricle), and a long neck terminated by a 4-lobed bell- 

 mouth ; the ventricle is immersed in the small-celled tissue, and is nearly filled by a 

 more or less spherical cell, from which, after fertilization, the new plant will start. 

 It is into the cavity of these little cushions that the autherozoids are said to pene- 

 trate to effect fertilization. 



