82 PRACTICAL BOTANY 



used instead of the Holly, the structure being very similar, with 

 the exception that the hypoderma and marginal sclerenchyma 

 are absent. 



"Water stomata and marginal glands. Examine leaves of the 

 Fuchsia, and observe that the tips of the leaves and the 

 marginal teeth are terminated by slightly swollen, opaque 

 masses of tissues : these are the marginal glands, and drops of 

 water exuded at those points maybe seen in the morning, or 

 on plants, kept during the day in moist atmosphere at a high 

 temperature. 



Cut off a piece of the margin of a leaf and examine it under 

 a low power : a large stoma (water-stoma) may be recognised 

 at the apex of each tooth : below it is a pad of opaque tissue 

 (the gland) to which a vascular bundle runs up, and in which it 

 ends. 



From material which has been hardened in alcohol, cut off 

 with a razor the extreme tips of several of these teeth : mount 

 with the outer surface uppermost : on examining these, the 

 extreme apex, with the water-stoma will be seen in surface 

 view. Note the size of the stoma, and that the pore is widely 

 expanded. 



Cut longitudinal sections so as to follow the vascular 

 bundle up to the marginal gland, and to traverse the gland in 

 a median plane. Selecting a section which is really median, 

 note, in the part of it further from the tip, the epidermis, 

 mesophyll} and the vascular bundle surrounded by a parenchy- 

 matous sheath following these up towards the tip, observe the 

 epidermis continuous, with the exception of the widely-gaping 

 water-stoma at the extreme apex : the form of the guard-cells 

 as seen in section is simpler than in ordinary stomata. The 

 vascular bundle widens out towards the tip, and the vascular 

 elements terminate in the pad of closely-packed parenchyma 

 of the gland (epituema) : there is a large cavity below the 

 water- stoma. 



Special attention should be paid to the chalk-glands of the 

 Saxifragacce (e.g. Saxifraga crustata) in which the structure of 

 the marginal gland is extremely well seen, while the accretions 

 of chalk deposited by the evaporating water are easily re- 



