88 MR. H. M. WARD ON THE STRUCTURE, DEVELOPMENT, 
Thea, Memecylon, Eugenia, Anona, Eleagnus, Magnolia, Citrus, Durio, Sideroxylon, 
Quassia, and Michelia. On several trees of the latter genus (Michelia fuscata), growing 
in the garden near my residence, the lichen was so regularly and abundantly developed 
that excellent opportunity and materials for the research were continuously present. 
The details to follow, therefore, are particularly true for this form, and must be held 
to apply generally to the specimens obtained from the other plants. I have been able to 
detect few differences (none of importance) in the other forms mentioned, and shall refer 
to such as are known as we proceed. 
Fig. 1*, Pl. XVIII., is an excellent representation of a twig of Michelia, the leaves 
of which are affected with the epiphyllous lichen in all stages of development. Careful 
examination of the various-sized spots and blotches enables one to distinguish about four 
types, differing chiefly in colour and consistency. These are, taken in proper (i. e. 
developmental) order of sequence :—(1) orange-red circular or stellate patches ; (2) green 
or grey-green blotches; (3) whitish or grey spots; and (4) glistening white shining 
circles, or irregularly branched groups. All these types pass by imperceptible gradations 
one into another ; and any one may vary in size from a mere point to a disk a quarter of 
an inch or even more in diameter. For the sake of simplicity and clearness, I shall 
describe the phenomena in genetic order as far as possible, and not in the sequence 
of their discovery. | 
If a leaf, such аз the upper one in fig. 1, be carefully observed during several weeks, it 
becomes clearly demonstrated that the orange-red and green types of the spots, of all sizes 
and shapes, pass over into the grey and white types; in other words, the red and green 
spots or blotches are earlier stages of the glistening white one, which is the complete 
Lichen (Pl. XVIII. fig. 3). As will be described later on, these changes may occur 
slowly or more rapidly, according to circumstances; hence the variations in size and 
form attained by any one stage prior to its passing into the succeeding condition. 
If the spots of fig. 1 be slightly magnified, one discovers that the orange-red patches 
consist of delicate branched or rounded cushions, of soft texture, and studded, more 
or less profusely, with radiating filaments of exquisite beauty (fig. 2). The greenish and 
grey types, similarly enlarged, present equally various outlines; but the filaments and 
orange-red tint have here disappeared, and crowds of minute black dots are embedded in 
the greenish-grey matrix or cushion. When the complete lichen (fig. 3) is closely examined, 
it appears to consist of a dense, opaque, white ground-substance, shining with a glistening 
lustre, almost like porcelain, in which are embedded crowds of black dots as before, toge- 
ther with a smaller number of larger black or brown bosses. | Asalready said, any of these 
types may vary in size, and may be circular, stellate, or irregularly branched in outline. 
I may anticipate matters so far as to say that the orange-red early stage (fig. 2) is an 
Alga, of which the radiating filaments are in part reproductive organs, in part barren 
hairs; that this passes over into the green and grey stages, the orange-red cell-contents 
becoming simultaneously changed in many cases to chlorophyll-green masses, while cer- 
tain modifications of growth «с. are induced by the invasion of a definite Fungus- 
* This excellent drawing was made by Mr. W. De Alwis, the artist at Peradeniya; and I take this opportuuity 
_ of thanking him for the care bestowed on it. 
