From the Edgar Rice Burroughs Timeline Bio: 
The 1920s Decade
May 1920: Ed assigns rights to an English theatrical company who produce Tarzan of the Apes and The Return of Tarzan as a stage play. Ed receives $1000 and 10% royalites, but the production meets with limited success. 
February 4, 1921: Arrangements are finalized to produce The Son of Tarzan in England under the same terms as last year's stage play. 
September 1, 1921: The English Tarzan stage play makes its US debut at New York's Broadhurst Theater. It has a short run. 
September 17, 1921: The Tarzan of the Apes play is reviewed in Weekly Review. 

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   Tarzan made its debut on the New York stage on September 1 (1921) at the Broadhurst Theater, Forty-fourth street and Broadway in New York. The advertised "Dramatic Version" presented by George Broadhurst was in four acts and ten episodes, with British authors Woodgate and Gibbons listed, and with staging by Mrs. Trimble Bradley. Members of the original British cast included Ronald Adair as Tarzan and Edward Sillward as Kala. Lady Greystoke was played by Alice Mosely, and Ethel Dwyer took the part of Jane. The play became more daring than the British version; Broadhurst had real lions on stage — two of them. Jim, the original Tarzan lion, and Beauty, the lioness, were noted as playing "silent but active parts."

The play, in its New York performance, found the public and critics unenthusiastic; its run was brief. To Bray, on September 20, Ed commented about the telegram he had received from George Broadhurst, which stated "the stage version of Tarzan of the Apes is a complete failure and that they are withdrawing it." Ed wrote:

From the newspaper criticisms which I received today I judge that there was no reflection upon the story and that it will do the books no harm. Most of the critics seem to think that the impossible has been attempted and I rather imagine they are right. However, it has been well received in England although it has never played in the West End of London. Broadhurst tells me that he believes he can send out a condensed version on the vaudeville circuit and personally I think it is better adapted to that than to the drama.

Astonishingly, for an author who had set high standards for a serious film production of Tarzan, Ed added, "My idea of a paying proposition for the stage based on Tarzan would be a real, honest-to-God Burlesque."

On October 19, in reporting that Tarzan was a failure in New York, the Curtis Brown office sent an evaluation:

From the accounts we have had of the production, it seems that it was an adequate one and the play was well cast, but in spite of that the play only ran a short time and all the returns have been sent to you. I am afraid there is little chance of the play going on the road as George Broadhurst feels that the production has shown it is not likely to appeal to American audiences... .

Ed's suggestion and apparent approval of an "honest-to-God Burlesque" was hardly an idea that the British producers would have endorsed. In an amusing 1921 sidelight in England, Gibbons and Carlton brought a court action against Dick Mortimer for his sketch, obviously a burlesque or parody of Tarzan, presented at the Victoria Palace in London. The sketch, titled "Warzan and his Apes," featured a cast of a man with a loin cloth, two actors dressed as apes, a pseudo-lion and a "property" baby. The jungle setting consisted of artificial trees and shrubbery. Certain scenes, copied from Tarzan, were done in "dumb show."

~ Porges - page 502

Broadhurst Theatre, (September 7, 1921 - Closing date unknown) 
Total Performances: ?
Category: Play, Melodrama, Original, Broadway

Opening Night Production Credits

Produced by George Broadhurst.
Book by Major Herbert Woodgate and Arthur Gibbons; 
Based on the novel "Tarzan of the Apes" by Edgar Rice Burroughs; 
Book adapted by George Broadhurst.
Staged by Mrs. Trimble Bradley.

Opening Night Cast

Ronald Adair: Tarzan, the man 
Alfred Arno: Kerchak 
Ford Chester: Parkinson 
Boyd Clarke: Bobby, Lord Greystoke 
Ethel Dwyer: Jane Porter 
Lionel Glenister: Lord Greystoke & Edward Ainslee
John Grattan: Tarzan, the child 
Minna Gale Haynes: Lady May Greystoke
Greta Kemble-Cooper: Lady Alicia Clayton 
Howard Kyle: Webb 
Lawrence Marks: Tarzan, the boy 
John F. Morrissey: Big Michael 
Alice Mosley: Lady Greystoke 
Forrest Robinson: Charles Porter 
Edward Sillward: Kala, the mother ape 
The credits for this production have not yet been completed or verified.

She had portrayed Tarzan's love in 14 performances, more than most of the "Jane" actresses have done, and received good reviews in major New York newspapers. 

Ethel Dwyer died of a heart attack on September 2, 1985, at her home in Pittsburgh, PA at the age of 86.

. Theatrical Life Before Broadway
Tarzan On Stage In England (1920-1921) 
From Porges - Page 501

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   Plans called for Tarzan of the Apes to be given a trial run in the provinces before the play was brought to London, and on October 4 it opened for a two-week stay at Brixton. (Producer) Gibbons had ten weeks' bookings to follow at other suburban theaters. At the Brixton opening, as reported by Curtis Brown, the audience was highly enthusiastic: "The jungle scenes were effective and proved distinctly to the taste of the audience. The parts of Tarzan and Kala were both played extremely well, Kala being particularly good."

In the play, with its prologue and four acts, the background and early events of the novel were developed. Surprisingly, Tarzan, age ten, was played by a young girl — Gwen Evans. Actors took the ape roles, Leon Du Bois playing Kerchak, the bull ape, and Edward Sillward in the part of Kala, the she-ape. They both continued their roles when the prologue ended, and the major section of the play presented Ronald Adair as Tarzan and Ivy Carlton as Jane. Adair appeared to be well-chosen for the difficult enactment of a live "stage" Tarzan.

On December 14 Ed was notified that the tour of Tarzan of the Apes in England would end that week, but that one performance of the play had been scheduled for London on Boxing Day, the day following Christmas. However, arrangements for this performance fell through, and Tarzan was never staged in London. The limited success of the play did not discourage Gibbons from proposing a contract for the production of The Son of Tarzan; the financial terms were the same, and Ed, on February 4, 1921, cabled his agreement.

Meanwhile, confusing on-again, off-again notices concerning Tarzan of the Apes were being dispatched. The play continued irregularly until June and was then halted because of the "industrial unrest . . . strikes and restricted transport" which hampered business and theatrical activities in England. Gibbons and Carlton still had plans to produce the play in London in the fall of 1921.