THE HORSETAILS. 47 



group. The branches, as in the evergreen species, are 

 produced from buds in the axils of the leaves in the 

 sheath, and these, as they develop, burst through the 

 base of the sheath instead of growing up out of it. 

 The branches are, of course, jointed like the stems, with 

 sheaths at the joints, and at their junction with the main 

 stem each is surrounded with a dark-coloured sheath of 

 its own which gives an additional girdle of colour to the 

 joints of the main stem. In the ordinary plant a few of 

 the lower nodes do not produce branches, while toward 

 the tip the whorls of branches are successively shorter, 

 forming a blunt-enclecl frond above which the stem con- 

 tinues for a short distance as a slender prolongation. 



As might be expected of a plant growing under such 

 diverse conditions of light, warmth, and moisture, there 

 is great variation in the form of the sterile frond. Mr. 

 A. A. Eaton has recorded no less than nine named forms 

 in the Fern Bulletin. None of these seem fixed, and 

 it is likely that all can be changed to the normal form by 

 a change in the soil or surroundings. The erect form 

 which we have taken as typical is mainly found in moist, 

 rich, light soil in half shade. The next most noticeable 

 form is named decumbens, and is characterized by the 

 main stem spreading along the ground with only the tip 

 erect. The short branches, however, are all erect, and 

 this makes a peculiar one-sided form easy to recognize. 

 It is common in exposed sterile soil and is usually to be 

 found on railway embankments. In the form called 

 diffusum there appears to be no central stem, the 

 branches arising from the summit of the rootstock and 

 spreading flat on the eartli. This is often found along 

 roadsides, and in other places, in the company of decum- 

 bens. PscudosylvatieuDi is a form in which the branches 



