HA RD WICKE 1 S SCIENCE- G OS SIP. 



229 



by means of the glands with which the leaves are 

 furnished. 



In the common butter wort {Pinguicula vulgaris) 

 the general form of these glands is disc-, or cheese- 

 shaped, somewhat resembling the fruit clusters of the 

 mallows, but perhaps thicker in proportion to the 

 circumference ; and there are four different develop- 

 ments of them, viz. three on the upper, and one on 

 the under surface of the leaf. Of the former, whose 

 functions are identical, the largest occur from the 

 lower mid- to upper part of the leaf, are nine to ten 

 hundredths of a millimetre, or about 5 1 5 of an inch in 

 diameter, '03 to '04 mm. thick, and are raised on 



Fig. 128. — X 260. 



Fig. 129. — x 260. 



flask-shaped unicellular pedicels about -15 mm. or 

 jfo of an inch high ; -03 mm. in diameter at the top, 

 and twice as much at the broadest part of the base, 

 which rests on a slight hemispherical elevation (Figs. 

 127 and 128). These pedicels are transparent, nearly 

 colourless, and stand about -2 mm. or T ^ 5 of an inch 

 apart. The gland itself is normally divided into 

 sixteen cells, which do not radiate from the centre, 

 but are the result of a successive subdivision of the 

 walls in the course of growth. Two first formed cell- 

 walls have intersected at right angles in the centre, and 

 afterwards branched off at various points, more or less 

 distant from it (Fig. 129 a). The subdivision some- 



times results in the production of seventeen to twenty 

 cells, some of which are not more than one-third of 

 the diameter of the disc in length (Fig. 129 b). If 

 taken from a clean leaf, the colour of the gland is 

 light green and quite transparent, so that when viewed 

 either from above or laterally, the top of the pedicel 

 can be seen through it. 



When by the processes of secretion and absorption 

 the gland has assimilated some of the food supply 



Fig. 130. — X 120. 



Figs. 131. — X 260. 



Fig. 132.— X 260. 



collected on the leaf, it presents the appearance 

 illustrated in another gland, viz. Fig. 131 b. 



The second description of glands are situated 

 towards the base of the leaf, and are similar to tile 

 above but smaller, being about *o8 mm. in diameter. 

 Their pedicels are larger, more inflated, one-celled on 

 the mid-lamina (Fig. 132) ; two to three-celled near 

 and on the mid-rib (Fig. 130). 



The smallest kind of glands occurring on the upper 

 side are thickly distributed over the whole surface of 



