XII 



EQUISETINEM 459 



of the sheath there is developed an axillary bud, which may 

 either at once develop into a shoot, subterranean or aerial, or 

 these buds may remain dormant for an indefinite period, being 

 capable of growing, however, under favourable conditions. 

 The surface of the rhizome in E. tclmatcia, especially at the 

 nodes, is covered with a dense dark-brown felt of matted hairs, 

 and a whorl of roots occurs at each node, corresponding in num- 

 ber to the number of axillary buds, from whose bases the roots 

 really grow. Sometimes the buds become changed into tubers 

 (Fig. 266), which are especially common in E. tclmateia and E. 

 arvcnse. These tubes are protected by a hard brown scleren- 

 chymatous rind, within which is a mass of starchy parenchyma, 

 traversed by the slender vascular bundles. In some cases these 

 buds form in chains and are then seen to be the swollen inter- 

 nodes of short branches. 



The aerial stems are of two kinds, sporiferous and sterile. 

 In one group the only difference between the two is that the 

 former bear at the apex the sporangial strobilus ; in the second, 

 of which E. tclmateia is an example, the sporiferous branches 

 are almost entirely destitute of chlorophyll and quite un- 

 branched, while the green sterile shoots are extensively 

 branched. In such forms the fertile shoots die as soon as the 

 spores are shed, and usually appear before the green shoots are 

 developed. 



The Stem (Rees (2) ; Sachs (i) ; Janczezvski {3) ; Jeffrey (2) ) 



A longitudinal section of one of the numerous subterranean 

 buds (Fig. 267) shows that the conical apex of the stem is 

 occupied by a large pyramidal cell whose segmentation is ex- 

 ceedingly regular. The youngest of the foliar sheaths is sepa- 

 rated from the apex by several segments, but below, the next 

 older sheath is very close to it,^and the internode, which in the 

 older stem is so conspicuous, is scarcely perceptible. The 

 closely-set sheaths grow very rapidly, so that all but the young- 

 est ones extend beyond the stem apex, which is thus very com- 

 pletely protected. They form a compact, many-layered cover- 

 ing about it, presenting very much the appearance of the leaf- 

 buds of many Spermaphytes. The apical cell shows the usual 

 three series of lateral segments. These are arranged in three 

 rows, but owing to a slight displacement in the younger ones, 



