These "rays" are given off by living organisms and are apparently of a different spectrum than the electromagnetic spectrum. Alexander Gurwitsch is a noted researcher on this subject.
Researchers:
De Sauer, Professor: Tompkins and Bird in their Secret Life of Plants, said on page 318 that De Sauer had actually discovered mitogentetic rays before Gurwitsch, who is usually credited with the discovery of these rays;
Gurwitsch, Alexander: 1920s and 1930s, famous researcher on this subject;
Bibliography and References:
Naumova, Elena V., Anna E. Naumova, Dmitry A. Isaev, and Ilya V. Volodyaev. "Historical review of early researches on mitogenetic radiation: from discovery to cancer diagnostics." Journal of Biomedical Photonics & Engineering 4, no. 4 (2018): 040201. Article has 186 references; Available at: Toshiba/Seagate EHD;