Former senator Forrest C. Donnell (R-Mo.), who was recognized as one of the ablest constitutional laywers in the Senate and also one of its most tiresome speakers, died Monday in St. Louis, Mo. He was 95 and had a heart condition.

Mr. Donnell, a lawyer by profession, served from January 1945, to January 1951. He had been elected to the Senate after serving a four-year term as governor of Missouri. The Senate seat had been vacated by Harry S. Truman, who had won election as vice president.

A stickler for abiding by the rules, Mr. Donnell was a week late in taking his Senate seat on Jan. 3, 1945. His reason:

"My term as governor did not expire until Jan. 8th," he explained. "I could have resigned, but that would not have been fair to the people of Missouri with whom I had a fixed-term contract as chief executive of the state."

That same strict adherence to the rules proved to be his undoing when he sought reelection to the Senate in 1950. He refused to leave Washington to campaign until the Senate adjourned. He never quite caught up with his opponent and was defeated by Democrat THOMAS C. Hennings.

Mr. Donnell was a sharp and loud debater during his years on Capitol Hill. He also was considered long-winded and tedious. He weighted every pro and con of an issue in his speeches, dragging them out with analogies, quotations, definitions and legal verblage.

Yet many of his fellow members of Congress admired his throughness in legislative matters, his honesty and sincerity.

During his tenure, Mr. Donnell won labor's enmity by backing the Taft-Hartley Act, and President Truman's displeasure by raising Cain about the latter's appointment of cronies to high office.

At the same time, Mr. Donnell made friends by supporting federal aid to education, slum clearance and housing measures.

Mr. Donnell was born in Quitman, Nodaway County, Mo. He graduated from the University of Missouri at Columbia and from its law school. He was admitted to the bar in 1907, and set up a practice in St. Louis.

Active in numerous legal, civic and church organizations, he became well-known throughout the state.

In 1940, the St. Louis Republican Committee asked him to run for governor of Missouri, although he was given little chance of success. Hardcore party workers gave him only token support.

Mr. Donnell, however, proved to be a persuasive orator and came through with an upset victory. It was then he became famous for his attempts to follow the letter of the law.

His accomplishments during his term as governor were few, but his oratory in 1944 once again brought him victory, this time to the U.S. Senate.

After his defeat in 1950, Mr. Donnell returned to his law practice in St. Louis.

He retired from the active practice of law at the age of 92, and in recent years had lived at a retirement home in St. Louis.

He is survived by a daughter, Mrs. Boyd Rogers, of Webster Groves, Mo.