EQUISETINEjE. 



393 



for a few days), show, when sown in water or on damp soil, the preparatory 

 phases of germination after a few hours. In the course of some days the pro- 

 thallium becomes developed into a multicellular plate, the further growth of which 

 then proceeds very slowly. The spore, which contains a nucleus and chlorophyll- 

 granules, increases in size as soon as germination commences, becomes pear-shaped, 

 and divides into two cells, one of which is smaller with scarcely any except colourless 

 contents, and soon developes into a long hyahne 

 root-hair (Fig. 274, /, //, III, w), while the 

 anterior and larger cell includes all the chloro- 

 phyll-granules of the spore which multiply by 

 division. This cell produces by further divisions 

 the primary plate of the prothallium, which in- 

 creases by apical growth and soon branches 

 (///- VI). The process of multiplication of the 

 cells is therefore apparently extremely irregular; 

 even the very first divisions vary ; sometimes 

 t:he first wall in the primary apical cell which 



contains chlorophyll is but little inclined with 



ispect to the longitudinal axis of the young plant 

 fn E. Telmateia 'it sometimes coincides with it) ; 

 other cases, on the contrary, this cell developes 



ito a longish tube, the apical part of v^hich is 

 ^ut off by a transverse septum (occasionally in 



r. arvense). The further growth is brought about 

 one or more apical cells dividing by trans- 

 ;rse septa, and longitudinal walls are subse- 

 quently formed in the segments in an order very 



lifficult to determine. Ramification takes place 



)y the bulging out of lateral cells, which then 



Continue their growth in a similar manner. The 



jhlorophyll-granules in the cells also increase con- 



inuously by division. The young prothallia are, 

 E. lebnateia, usually narrow and ligulate, and 



Consist of but a single layer of cells. The older 



>rothallia are, both in this and in other species, 



branched in an irregularly lobed manner ; one of 



le lobes takes, sooner or later, the lead in growth, becomes thicker and fleshy, 

 )nsisting of several layers of cells, and puts forth root-hairs from its under side. 



The prothallia of the Equisetaceae are, in general, dioecious. The male pro- 

 lallia remain smaller, attaining a length of a few millimetres, and produce archegonia 



mly in exceptional cases on shoots of later origin (Hofmeister). The female 



Fig. 274. — First stage of development of the 

 protha liuni of Equisetutn Tehnaieia ; tv the first 

 root-hair; t rudiment of the prothalliuin. The 

 order of development follows the numbers/— K/ 

 (X about 220). 



ler Wurzeln (Beitr. zur wissen. Bot. von Nageli, Heft IV. Miinchen i867>.— Pfitzer, Ueber die 

 jchutzscheide (Jahrb. fur wissen. Bot. vol. VI. p. 297).— Russow, Vergl. Unteis. iiber die Leit- 



indelkrypt. Petersburg 1872, p. 41. — Janczewski, iiber die Archegonien, Bot. Zeit. 1872, p 420. 

 ''an Tieghem, on the roots, in Ann. des sci. nat fth series, vol. XIII.— -[Sadebeck, Ueb. die Entwicke- 



ing der Prothallien der Schachteliialme, Bot. Zeit. 1877.] 



