EQUTSETACEM. 



3^5 



to be composed of four cells arranged like die quarters of a sphere. The same 

 author states that the foot, which he terms in this case also the primary axis, arises 

 from the lower quarter, the rudiment of the first shoot from one of the lateral 

 ones, turning upwards immediately afterwards and producing as the rudiment of 

 the first leaf a projecting girdle, w^hich then grows out into three teeth (Fig. 272 

 B). The first root now {?) arises from an wner cell of the tissue. It may here 

 be remarked that this observadon of Hofmeister's would establish, on the one hand, 

 an essential difference between the mode of formation of the first root in Equi- 

 setaceae and in other Vascular Cryptogams ; while, on the other hand, the origin of 

 the first leafy axis from one of the quarters of the embryo corresponds to the 

 behaviour of Ferns and Rhizocarps, and hence does not agree with the other pro- 

 cesses of growth of the Equisetaceae, since in all of them the other shoots are 

 developed from inner cells of the tissue. Duval-Jouve maintains, in fact, in oppo- 

 sition to this view, that the first leaf- 

 bearing axis has a lateral origin in the 

 interior of the already muUicellular em- 

 bryo, so that even the first shoot of 

 Equisetum would be of endogenous 

 origin. The unaccountable errors of 

 this writer on the subject of apical 

 growth render his statements of but 

 little value in contrast to those of 

 Hofmeister ; the question is however, 

 in any case, deserving of further in- 

 quiry. 



The first leaf-bearing shoot grows 

 upwards, and forms from ten to fifteen 

 internodes with sheathing leaves end- 

 ing in three teeth. It soon produces 

 at its base a new stronger shoot with 

 four-toothed sheaths (as in I^. arvense, 

 praiense, and variegatum^ according to 

 Hofmeister), which in turn gives origin 



to new generations of shoots, developing constantly thicker stems and sheaths 

 with a larger number of teeth. Somedmes the third or one of the succeeding 

 shoots penetrates downwards into the ground, forming the first perennial rhizome, 

 which again produces from year to year new underground rhizomes and ascending 

 leafy shoots. 



In order to facilitate the understanding of the Mode of Growth of the Stem and 

 Leaves, it is necessary to glance in the first place at their structure in the mature state. 

 Every axis of an Equisetum consists of a series of joints (internodes) usually hollow 

 and closed at their base by a thin septum. Each internode passes upwards into a 

 leaf-sheath embracing the next internode, the sheath being split at its upper margin 

 into three, four, or usually a larger number of teeth. From each tooth of the 

 sheath a fibro-vascular bundle runs vertically downwards into the internode as far as 

 the next node, parallel wdth the other bundles of the same internode ; at the lower 



Fig. 272. — Development of the embryo oi Equzsetum arvense 

 (after Hofmeister); A archegonium cut through vertically 

 with the embiyoy (X 200); H embryo further developed and 

 separated, b rudiment of a leaf, s apex of the first shoot (X 200) ; 

 C vertical section of a plate of a prothalliuni //, with a young 

 (asexual) plant, w its first root, bb' its leaf-sheaths (X 10). 



