26 VASCULAR TISSUE. 
the bark or root, and in no flowerless plants, excepting 
Ferns (Filices), and Club-mosses (Lycopodiacee). Plants 
have been divided into two great classes— Vasculares, plants 
with spirals, and Cellulares, plants in which that 
form of vessel cannot be detected. Their average diameter 
is about 1-1000th of an inch ; but they are frequently larger 
or smaller. They contain gaseous fluid, said to be a 
with about eight per cent. more oxygen than is found 
atmospheric air. 
67. The spiral vessels may be observed in many plants b 
tearing the leaves gently. In the leaves of several kinds. 
Amaryllis, they may be easily detected, or in the Straw 
leaf or its stalk. They are abundant in the stems of 
Banana and the Plantain. 
68. Ducts, False Spirals, or Sap-vessels. These are’ 
modification of the spiral vessel, having transverse streaks 
or dots, or a sort of net-work, on their sides, arranged in 
somewhat spiral manner; but the tube is not capable of 
being unrolled like the true spiral. These appearances on 
the sides of the ducts are most probably owing to the vari 
ties in the course or mode of attachment of the spiral fi 
along the membrane forming the side of the tube. ‘Some 
s ‘are true spirals at one part, and false spirals or ducts 
_ at another. They are found in the wood in flowering plants, 
and in Ferns and ari acandaaecsieoes co 
69. Notwithstanding the infinite variety in form a1 
ture observed in the various organs of the objects which « 
pose the vegetable creation, they all consist of these 
tissues, which, by their union in various ways, form ¢ 
distinct parts (familiar to every one as separate parts of 
ee 
Seed. These may be called secondary, compound, 
Se ccenmreaeminn at 
—— Es 
