VEGETATIVE PROPAGATION 



the Filmy Ferns of tropical forests, an atmosphere approaching complete 

 saturation with moisture is a constant necessity. The Male Fern may 

 indeed be accepted as a medium type, showing no special adaptation 

 nor susceptibility either to moisture or drought, while structurally it 

 shows such characters as are usual 

 in average Land Vegetation. 



With very few exceptions Ferns 

 are perennials, and in the case of 

 the Shield Fern there is no theoretical 

 limit to the duration of the individual 

 life : in point of fact the plant may 

 grow continuously for a long term 

 of years, as is shown by the length of 

 the stock, and the long succession 

 of the bases of leaves of former years 

 which may be observed persistent 

 upon it in the larger specimens. But 

 still it is subject to many vicissitudes, 

 which are liable to terminate its exist- 

 ence. Some provision must be made 

 for the maintenance of the race by 

 the formation of new individuals. 



The vegetative mode of propaga 

 tion in the Shield Fern is by means 

 of buds which appear at a late period 

 upon the persistent bases of leaves of 

 former years. These develop leaves 

 similar to those of the parent, with 

 roots which form an independent 

 system, so that when the progressive 

 rotting, which is always advancing 

 from the base of the stock onwards, 

 isolates the parent leaf from the rest 

 of the plant, the bud is in a position 

 to subsist as an independent individual 

 (Fig. i, B, c). This is merely one 

 example of what is a very common 

 phenomenon in Ferns, viz. the vege- 

 tative propagation of the individual. 

 The details of the process, such as 

 the position and the number of buds, may vary greatly in different 

 cases (Fig. 3), but the essential point is the same, that by a purely 

 vegetative growth, and without any known cytological complications, 

 new individuals may be derived, which are similar in all essentials to 

 the parent. Such means of increase are styled collectively under the head 



Cystopteris Inill'i/i-fn (I,.) liernh. /4, part of a 

 leaf with adventitious buds. Natural size. B, an 

 adventitious bud which has fallen off, forming a 

 root. C, an adventitious bud further developed. 

 B and C somewhat enlarged. (After Matouschek.) 



