Some species, as silvaticum, bear verticils of branches just 

 below the sheaths of the upper internodes. When present the 

 branches are simple, save in a few species, as silvaticum, pra- 

 tense and occasionally arvense. They are of essentially the same 

 structure as the stem, except that in some species they want the 

 central cavity. In no species of Equisteum proper do they habit- 

 ually bear spikes, but may do so in all, giving rise to the polysta- 

 chyum (many spikes) varieties. The branches of the larger Hip- 

 pochaetae often bear spikes with us, and regularly do so in Mexi- 

 can and South American species. 



At a depth of one to three feet in the soil there is a horizontal, 

 wide-spreading, repeatedly-forked rhizome, composed of inter- 

 nodes with their sheaths much like the aerial stems. Back of these 

 sheaths there are verticils of roots, corresponding to the branches 

 above. Besides this, the rhizome is usually clothed with a cinna- 

 mon-colored felt of root-hairs. In some species, as arvense and sil- 

 vaticum, some internodes are shortened and thickened, forming 

 tubercles, which are often in series like a string of beads. Their 

 office is unknown, and it is doubtful if they are of any economic 

 use. 



The rhizome is the essentially perennial part of the plant. 

 Any fragment will develop into a new plant, if properly situated. 

 At intervals they give rise to secondary rhizomes, which ascend to 

 the surface of the earth, where they produce buds which develop 

 into aerial shoots. These buds, before growth commences in 

 spring, are simply a collection of sheaths and teeth. Growth 

 consists of the lengthening of the internodes, which shoot out like 

 the joints of a telescope. They do not increase in diameter at all 

 as they develop. 



The secondary rhizomes are usually from six inches to two 

 feet in length, but it seems impossible to bury the plants so deeply 

 that they will not find their way out. I have seen arvense and 

 silvaticum flourishing and fruiting from the top of a sawdust pile 

 seven feet deep the second year after being covered. 



The spikes are normally terminal on the main stem, raised on 

 a short, flesh-colored peduncle. Usually there is a ring just be- 

 neath it, which is easily shown to be a modified sheath, sometimes 

 with normal teeth, and even with a verticil of branches below, as 

 occasionally in silvaticum. 



The spikes are composed of whorls of little buckler-shaped 

 objects (clypeoles), consisting of a short pedicel and a five or six- 



