496 
Fig. 20. 
Fig. 21. 
Fig. 22. 
Fig. 23. 
Fig. 24. 
Fig. 25. 
Fig. 26. 
Fig. 27. 
Fig. 28. 
Fig. 29. 
Fig. 30. 
Fig. 31. 
Mr. VALENTINE on the Structure and Development 
Tak. XXXV. 
The termination of a growing branch, with two young leaves and 
four roots in various stages of advancement. a. Is a root before it has 
burst through its sheath. 6. The sheath which envelopes the tip 
of the root. c. À young bud, from which may be produced either a 
branch and leaves and roots, or an involucrum: it is impossible to 
distinguish one bud from the other in the youngest state. All the 
buds and growing extremities of the branches are clothed with hairs, 
which fall off as the part becomes developed. 
An involucrum about half matured; it is densely covered with hairs, 
which gradually decay and fall off, so that there are only a few de- 
cayed remnants left on the mature involucrum. 
À hair from an involucrum. a. The point of attachment. 
A hair from a bud. a. The point of attachment. 
Section of a leaf, showing the central bundle of vessels surrounded by 
enlarged cells; the partitions, and a diaphragm. 
Section of a root, showing two of the gyrate bodies, which are fre- 
quently found in the cavities of the root. 
A portion of the cuticle of the leaf with stomata. 
Longitudinal section of a leaf, giving a view of a partition, and the 
central bundle of spiral vessels. 
A portion of the tissue which forms the partition in the root. 
Section of a young involucrum. In this stage the three outer coats 
are of a very faint brown colour, and the inner quite colourless. The 
two middle coats are drawn scarcely thick enough. The theca 
contain sporules in the first and second stage of development ; they 
are too opake, however, to show their .contents with any distinct- 
ness. 
Section of a mature involucrum from about the middle, so that it 
contains both kinds of thecæ ; those containing fertile sporules, and 
those which are occupied by the abortive ones. 
A union of sporules in their first stage; the mother-cell is not visible 
in this stage :—magnified 200 times. 
