93 



ESSENTIALS OF VEGETABLE PHARMACOGNOSY. 



Intorruptedly-piuuate or riunatifid. When 

 the leaflets or divisions are turned back- 

 ward so that they point more or less iu the 

 direction of the base (Fig. 4G8), the leaf is 

 Runcinate. When the terminal division is 



Another form is the well know^n Venus' 

 fly trap (Fig. 471), which secretes a nectar 

 by certain glands w^hich surround its mar- 

 gin. The insect alighting upon tliis point 

 is instantly seized through the spasmodic 

 coming together of the two lateral halves 

 of the leaf, which act precisely like the 

 jaws of a trap. Thus secured, digestive 

 fluids are immediately poured forth from 

 special glandular tissues on the leaf sur- 

 face and digestion and absorption take 

 place. That tlie nutrients thus absorbed 

 are of service to the plant has been proven 

 by elaborate experiments, in which the 



verymuch larger, especially broader, than ^ff^..^, ^^ ^^^^ f^.^i ^^^^ ^^^^ ^^^_ 

 the lateral, the leaf is Lyrute (Fig. 4G9). 



Coming now to consider the subject of 

 characteristic modifications in the form 

 and function of the leaf, we note that 

 some of them refer to the entire leaf, 

 others to its individual parts. We also 

 note that in some of the modifications the 

 entire leaf or one of its parts retains the 

 ordinary functions of. absorption and as- 

 similation, the new function being added 

 thereto either by partial change of the en- 

 tire leaf, or the complete modification of 

 one or more of its parts, while at other 

 times the original functions are entirely 

 suppressed. 



The function of absorbing and assimi- 

 lating the ordinary forms of nutriment is 

 sometimes supplemented by that of ab- 

 sorbing and assimilating animal tissue. 

 In this case the leaf provides special forms 



of apparatus for enticing, intoxicating or 

 mechanically catching, kilhng and digest- 

 ing the animal, commonly an insect One 

 of these forms is illustrated in the pitcher 

 plant (Fig. 470), in which one portion of 

 the leaf becomes converted into a vessel 

 containing liquid of variable origin and 

 complex composition. Upon the outer por- 

 tion of the pitcher a line of glandular tis- 

 sue stretches downward. The insect 

 feeds upward along this line of secretion 

 which so changes its nature toward the 

 apex of the pitcher, that at the time that 

 the msect reaches that point he is more or 

 less mtoxicated, and on crossing the mar- 

 «rin, or quickly thereafter, falls into the 

 liquid and is drowned, digestion promptly 

 occurring by means of enzymes excreted 

 into the liquid by special glands located 

 upon the inner face of the pitcher. 



...Ir 



- a 



mated and compared with the reproduc- 

 tion by other similar plants, similarly 

 treated in all respects except that they 

 were deprived of this form of food. 



In other cases the plant being nourished 

 by means of fully prepared nutrients ab- 

 sorbed from other leafy plants (host- 

 plants) upon which they are parasitic, the 

 leaves lose the chlorophyll tissue upon 

 which their ordinary functions depend 

 and are known as Etiolated leaves. They 



become reduced in size and scale-hke in 

 form. 



