1. Situation is said to be critical.
2. These types of Nouns are said to be in Possessive Case
In these two sentences a special phrasal verb construction "to be said to" is used.
It is similar to the verbs "to be supposed to" and "to be alleged to".
The verb "to be said to" indicates a reported fact or an alleged fact that the writer/speaker may not be certain about.
It can be followed by "be" or another verb
These raincoats are said to be waterproof.
A genie is said to live forever.
The man is said to have been arrested by the police.
3. These trees are not to be found elsewhere.
In this sentence the infinitive "to be" is used to express the future.
These trees are not found elsewhere...........You can't find these trees elsewhere.
These trees are not to be found elsewhere......You will not find these trees elsewhere.(even if you look)
"To" can be used with other verbs to express the future.
The president is to leave the capitol tonight........The president will leave the capitol tonight.
Or in newspaper headline style: .... President To Leave Capitol Tonight