composed of

"In one of the lithographs a crowd of these good dull people are looking at the blossom of a night-blooming cereus, the extraordinary attributes of which are loudly proclaimed by a showman. In the craning heads, in the gaping mouths, in the vacant eyes, in the forced self-conscious wonder and admiration of the group we read without difficulty how superficial their sentimental is, how largely composed of a vulgar curiosity and desire merely to plume themselves upon having seen something that all the world does not see every day."

1. Please tell me what "the forced self-conscious wonder and admiration" means in the context.

2. Please help me to understand the blue clause.

Thanks in advance

Cadzao