CUYPTOGAMIA EQUISETACE^E. 



lowish cone-shaped catkins. These are succeeded by the 

 sterile plants, which rise to the height of 2 or 3 feet ; and 

 the crowded patches which they form, bear much resem- 

 blance to a plantation of firs in miniature. 

 The structure of the Equiseta is very beautiful. Fig. a. Tab. 

 V. is a view of a section of the stem of the species before 

 us, and Fig. b of the same plate is a similar view of the E. 

 arvense. Around the hollow centre there is a circle of 

 small canals, and external to that another circle of much 

 larger ones placed in an alternating order. The number 

 and relative size of these canals vary in each species ; but 

 the number in both circles of any specimen is always the 

 same, and they correspond pretty exactly to the number 

 of branches in a whorl. They are separated from one ano- 

 ther by a cellular tissue or web, each circle, however, being 

 in distinct layers, for although there is apparently no line 

 of distinction, they can be separated with ease. The ca- 

 nals run through the stem in a straight line, neither giving 

 off branches, nor communicating by anastomosis ; nor is 

 the continuity of the tubes interrupted by the septa which 

 divide the centre of the stem into regular compartments. 

 That this is the case may be proved by an easy experiment. 

 If after the root and top is cut away, we insert one end in 

 water, and suck through it, as boys do when they drink 

 through a straw, the fluid will rapidly ascend to the mouth. 

 In this experiment, the fluid ascends probably by the ca- 

 nals of the outer circle ; but a careful dissection will shew 

 the canals of the inner circle to be equally uninterrupted. 

 The outer canals communicate also with the branches, for, 

 with a fine syringe, I have succeeded in forcing water 

 through one of them into the adjoining branch. The ex- 

 periment does not always succeed, because the water finds 

 an easier escape from the opposite end of the stem. The 

 epidermis of some species (E. sylvaticum) is marked with 

 the oblong apertures of pores arranged in parallel lines, but 

 in E.flumatile these are not visible. The external canals 

 contain only air ; the inner probably convey the fluid ne- 

 cessary to the growth and nourishment of the plant. The 

 whole structure is very analogous to that of monocotyle- 

 donous plants, of the grasses or canes in particular ; and it 

 seems very obvious that the Equiseta must grow in the 

 same manner. De Candolle, however, is almost the only 

 author who has associated them with this family ; and in 

 common with others, he places them next to Ferns, which, 

 in a natural system, is perhaps a questionable arrangement. 

 In the true Ferns the stem is solid, and there is no ap- 

 pearance of open canals disposed in circles. On the con- 



