Page:The Journal of Indian Botany, Volume III.djvu/155

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Ashby, Edwin ; Sensitive labellum In orchids. The following account taken from the published minutes of a meeting of the Linnean Society on May 4th t may be of interest.

“ MR. Edwin ASHBY exhibited pressed specimens of Orchids from bouth Australia including a number of the “ spider-like *’ members of the genus Gcdadenia, and the green-hooded forms of the genus Pterostylis : many of these have a sensitive labellum which on the entrance of an insect closes up the entrance for a short period ; Mr. Ashby suggested that this was for the purpose of fertilization, A member of the genus Thelymitra, which only open their bright-coloured petals in hot bright sunshiny days, and two species of Galeya were exhibited, both extremely local in that state, and both provided with a sensitive labellum, which, on being touched, folds up in two separate movements.”

Turner Charles, F C.S. The life-Bisfcory of Staurastrum Dickie! var. parallelism (Nordsfc.). The following has been published as an abstract by the Author of a paper read before the Linnean Society of London, 6th April, 1922,

The want of rain, and the subsequent partial stagnation of the pools left by the side of a mountain stream in Denbighshire, was probably the cause of the very great number of zygospores produced by this desruid during the summer of 19*21 : fully one hundred of these were present on one microscope slide exhibited, in addition to the zygospores of two other [species associated with them.

It was observed that the contents of the spores was, at first, of an oily character and that this circumstance rendered the early stages of the nucleus difficult to trace. During the later stages the production of four nuclei in the spore is readily visible, before its germination : this apparently indicates that the process of conjugation resulted in the formation of a diploid nucleus, and that a reduction division occurred inside the spore before the discharge of its contents. This early formation of “ Desmid Mother-Cells ” is frequently seen, and the germination of the spore results in the formation of four, three, two, or one desmid only, usually accompanied by an atrophied nucleus in the surrounding protoplasm when the smaller numbers are formed. The protoplasm is subsequently assimilated and the desmids go free.

The process of conjugation is usually of the normal type, and the zygo- spores are produced between the two desmids without the formation of a conjugation tube ; but in one instance the occurrence of this rather uncom- mon condition was observed and a conjugation tube about 30 p in length and IQ /■*- in diameter was seen. The conjugating desmids were asymmetrically