LEAF-BLADDERS IN EICHHORNIA SPECIOSA. 221 



not produce such a large number of axillary shoots, nor do they 

 exhibit such a pronounced rapidity of growth as is seen in the 

 other plants. The transitional forms are shown in the diagram below. 



Physiology : — In order to find out the behaviour of the plant in 

 culture, I had a bladderless plant transferred to a jar containing the 

 necessary salts dissolved in rain water according to Crone's formula. 

 The appearance in a few days of swollen leaf stalks suggested that the 

 chief stimulating factor was water and an examination of both blad- 

 dered and bladderless leaves would, it was thought, disclose either 

 some difference in the water content or some sort of constitutional 

 change brought about by the excess or deficiency of water. It is well 

 known that stomata regulate their openings according to the amount of 

 water present in the transpiring organs and thereby prevent too much 

 loss of water from plants. A greater water content will thus keep 

 them open whereas a diminished supply will tend to the closing of the 

 aperture. A highly useful method -of ascertaining the width of the 

 stomat.il opening is afforded by the work of Ujin (fi) on the regulation 

 of stomata. This author and Lloyd have shown that simultaneously 

 with the opening of the stomata, the starch present in the guard cells 

 disappears in some way probably by enzymic activity in the presence 

 of a greater quantity of water and increases again when the water 

 becomes less, as happens for instance during the day when transpi- 

 ration gets more and more intense. As open stomata are sometimes 

 found even in'wetted plants, the appearance of starch does not so much 

 indicate the closure of the stomata as a diminution of the water 

 content in the guard cells and the leaf as a whole. By employing 

 chloral-hydrate-iodine as a delicate test for starch, I examined the 

 stomata of both kinds of leaves at different times during the day. The 

 corresponding youngest leaves were chosen and the results which were 

 confirmed by repeated observations are as follows, the drawings 

 having been made with the help of the Zeichen Apparate. 



The conclusions arrived at are : — 



(1) that young leaves with bladders or with a tendency to blad- 

 der showed very little starch in the guard cells of the stomata which 

 indicates a high-water content in the leaf. 



(2) that leaves without bladders always contained more starch 

 which is doubtless a response to the low-water content of the leaf. 



It thus appeared possible that the bladders could be induced to 

 form by making the water a\ailable to its utmost capacity, and I 

 succeeded in this by growing a plant without bladder in Crone's solu- 

 tion of low concentration, viz., 1 in 1000. Plants were also grown 

 in Sach's solution of normal concentration and in tap-water of the 

 aboratory which is relatively higher in salts. The latter showed no 



