Chapter X —129— Drosera 



the dilution of the applied material by the secretion of the glands 

 during the beginning period, and to equiHbrium during the later period. 



All substances are not absorbed at equal rates. Darwin noted 

 that they did not procure aggregation at the same rate. Oudman 

 found that caffeine is much more rapidly absorbed than asparagin, 

 although the latter has the smaller molecule. This may be due to the 

 path taken. Caffeine enters the vacuole and is there precipitated, and 

 fresh caffeine must traverse the zone of precipitation. Asparagin 

 probably passes along the path provided by the protoplasm. By 

 following the localization of fluorescence it was shown that fluorescein 

 does this. If the tentacles are removed, leaving the stalks open at the 

 outer end (due to the operation), less material is absorbed, but the 

 difference is not related to the exposed surface, it being much greater 

 for tentacles with the glands removed. The glands therefore offer 

 some hindrance, perhaps because they are quite complex organs, excreting 

 at the same time as absorbing. The presence of an endodermis (the 

 parenchyma bell, Fenner) may have some regulatory effect, but this 

 is not known to be the case. It is worthy of note that narcosis (with 

 ether) inhibits the penetration of asparagin more than caffeine, the 

 former traversing the protoplasm, the latter the vacuole. Caffeine is 

 known to penetrate into the vacuole with great rapidity (Bokorny, 

 Akerman, Erna Janson) and in any event it has to pass only a thin 

 layer of cytoplasm while asparagin is forced to pass lengthwise the 

 cells within the cytoplasm. 



In a later paper by Arisz and Oudman (1937), making use of an 

 improved method of applying the reagents to the tentacles, Oudman's 

 figures describing the rate of absorption of caffeine and of asparagin 

 were confirmed. Caffeine is absorbed in the fashion of a physical 

 diffusion, while asparagin shows a maximum penetration in the second 

 period, and low rates in the first and third periods. Nevertheless more 

 asparagin penetrated into the leaf blade as shown by tests after the 

 removal of the tentacles before analysis. It seems obvious that the 

 conclusion that the paths followed by these substances are different is 

 justified, namely that caffeine travels by way of the vacuoles and 

 asparagin through the cytoplasm, yet in spite of the narrowness of the 

 path through the cytoplasm, the latter moves more readily. This again 

 seems to be due to the taking up of the caffeine by precipitation, a 

 subsequent wave of diffusion having to overstep the zone of pre- 

 cipitation. 



An attempt was made by Arisz and Oudman to determine the in- 

 fluence of aggregation upon the transport of asparagin. Aggregation 

 was first induced by suitable reagents (sahcin 0.25% and KH2PO4 

 0.1% solutions) with a "remarkable result" that now more asparagin 

 was taken up during the first period (contrary to the above mentioned 

 rates). Since asparagin itself causes aggregation, during the first 

 period aggregation takes place, and during the second period, ag- 

 gregation now having taken place, penetration goes on more rapidly 

 because of this earlier induced aggregation. This behavior, that is, 

 aggregation, has on the other hand no effect on the rate of transport 

 of caffeine. 



Reproduction by seeds and by buds {"regeneration''). — While Dros- 



