Plantas carnívoras gigantes são uma característica comum da ficção científica, e os autores comumente as dotam de tentáculos para pegar presas. Eu não encontrei uma correspondência exata para sua história, mas você diz que é uma história antiga e menciona viajar para outra dimensão, e isso imediatamente me faz pensar em Clark Ashton Smith ou em outros escrevendo no mesmo estilo. Ele era excessivamente apaixonado por aventuras em outras dimensões - freqüentemente elucidam dimensões.
Existe uma árvore semelhante à sua descrição em sua novela Marooned in Andromeda , embora como o título sugere que isso não ocorre em outra dimensão, mas sim em um planeta na galáxia de Andrômeda. Eu li na antologia Other Dimensions vol 1 quando tinha uns dez anos e adorei - eu ainda possui esse mesmo livro:
De qualquer forma, a cena com a árvore é:
Adams ventured to take a step forward. Instantly a long tentacle shot out from the nearest of the kraken-like forms and encircled him. Struggling and screaming, he was drawn toward the great dark lumpish mass from which the tentacles emanated. There was an open cup-like mouth of vermilion, fully a yard wide, in the center of this mass; and before his companions could even move, Adams was thrust into the mouth, which forthwith closed upon him like the mouth of a tightened sack. Roverton and Deming were petrified with horror. Before they could even think of stirring from where they stood, two more of the tentacles shot out and gripped each of them about the waist. The grip was firm as an iron rope; and both were conscious of a sort of electric shock at the contact—a shock which served to stun them still further. Almost fainting, they were held erect by the horrible coils.
Nothing more happened for a brief interval. The incomprehensible strangeness of their position, the manifold fatigues and ordeals of the day, together with the shock of those coils, had dazed the two men so that they could hardly grasp the fate of their companion and their own imminent doom. Everything became unreal, misty, dream-like. Then, through the vagueness that enveloped their senses, they saw that the dark mass at the core of the tentacles was beginning to move and heave. Soon the heavings turned to convulsions that became more and more violent. Roverton and Deming fell to the ground as the coils loosened their hold, and saw the lashing of a score of tentacles in the air above, tossing from side to side about the agitated central mass. Then, from this mass, the body of Adams was ejected, to fall beside Roverton and Deming. Obviously human flesh had not agreed with the digestion of the Andromedan plant-monster. The mass continued to heave and palpitate, and its myriad arms waved through the air as if in agony
Mesmo nos anos 70, as histórias de Clark Ashton Smith foram encontradas principalmente em antologias, e eu me pergunto se você pode ter lido a história em uma antologia e confundi-la com outras histórias dele sobre diferentes dimensões. É um tiro longo, mas achei que valeria a pena tentar.