THE GENUS EQUISETUM 



A prerequisite to the effective study of any of these species is a fairly detailed know- 

 ledge of its coning habits. In a few cases cones could be obtained in culture,* but in a 

 greater number very close observation of wild populations was needed as the only means 

 of obtaining suitable fixations at the right time of year. Since the knowledge so gained 

 may perhaps be of interest to field collectors, being of a kind not easily obtained from 

 books, it may perhaps be of interest to append a few notes about it before considering 

 the cytological results. The seasons at which successful fixations were actually taken may 

 be listed f as follows : 



Species Locality 



Subgenus Eu-equisetum 



Month of meiosis 



At first sight these dates may appear somewhat arbitrary, but it is not difficult to 

 correlate them with some fairly simple general habits of the various species. Thus all 

 those species with deciduous aerial shoots on which the cones are also borne will show 

 young sporangia with maturing mother cells on the newly emerging green stems in the 

 spring, that is, in about the month of May in Great Britain. The principal representa- 

 tives of this type are E. palustre and E. limosum (cf. Fig. 5, p. 18), in both of which the 

 young cones can indeed be found in the resting buds of the previous autumn but only 

 in a very immature condition. The non-deciduous species, e.g. E. hiemale, E. variegatum, 

 E. Moorei, E. trachyodon, and probably E. scirpoides — though I have not seen this non- 

 British species in its native haunts — mature their cones later in the summer or during a 

 longer season. Thus meiosis can be obtained under normal climatic conditions in all of 

 these species at the end of August, though in some, notably E. variegatum and perhaps 

 E. hiemale, a continuous succession of new shoots, some of them bearing cones, may be 



* Most of the species listed may be grown easily in ordinary garden soil without any special treatment 

 except reasonable freedom from desiccation. My own plants were grown in the ground in an unhealed 

 partially shady fern-house, the only precaution taken being to enclose them in brick compartments 

 lined with cement to prevent the rhizomes from escaping into other parts of the house, since they 

 become very troublesome weeds if allowed to become rampant. Under these conditions vegetative growth 

 was luxuriant but cones were rare, probably through lack of light. The small species, e.g. E. scirpoides 

 and E. variegatum, wall, however, cone quite readily in pot culture, and E. limosum coned annually when 

 grown in a large pot submerged in an artificial pond. It is probable that E. palustre might do the same 

 though this species was not actually grown. 



t The classification adopted here is primarily that of Milde (1867). 



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