December, 1922. 



The Canadian Field-Naturalist 



171 



The Spruce gall is perhaps the best known, 

 though novices often mistake it for a cone. The 

 maker of this gall spends one half of its life history 

 on Spruce, and the other half on Douglas Fir, and 

 in its two stages may be mistaken for two different 

 animals. 



The large knotty growths on branches of the 

 Thimble berry are caused by another type of gall 

 maker related to the Saw-flies and Ichneumon 

 flies, known as gall flies (Cynipidae) . Then on 

 leaves we find the Spangle galls. Currant galls, and 

 Apple galls formed by Cecidomyia and other allied 

 insects. Perhaps the most beautiful result of such 

 infections is to be seen on leaves of the Mountain 

 Maple, where the upper surface is beautifully 

 marked or streaked with carmine, red, or crimson . 

 I have seen such diseased trees transplanted to a 

 garden because the leaves were more beautiful 

 than the leaves of the healthy trees, and I once 

 received specimens of diseased shoots of this Maple 

 from a correspondent who thought he had found 

 a new variety. 



This reminds me of a somewhat amusing 

 experience I had about ten years ago. An en- 

 thusiastic amateur botanist called at my office 

 with specimens of one of our native roses {Rosa 

 gymnocarpa), the Naked-fruited Rose, which, 

 instead of the small globular fruits, had enlarged 

 pear-shaped fruits. My friend was convinced 

 he had discovered a new variety and desired my 

 opinion before he published a description of it 

 under the varietal name pyriforme. At his 

 request I visited Kitsilano, where these roses 

 grew, and, although most of the rose-fruits were 

 pear-shaped, I found some bushes bearing both 

 globular and pear-shaped fruits. This aroused 

 some doubt in my mind as to the validity of the 

 proposed variety pyriforme. I made a col- 

 lection of seed for the botanical garden, to see 

 if the offspring would bear similar fruits. I also 

 retained a supply of seeds for the seed-collection 

 in my office. 



The foUow'ng year the gardener informed me 

 that not one single seed of this rose had ger- 

 minated; he asked if I could let him have some 

 more. On inspecting the supply in my seed 

 collection I discovered that every seed had a little 

 hole in it, and along with the seeds I found a large 

 number of small gall-flies. The pear-shaped 

 fruits were diseased ones, they had all been galled 

 by these tiny flies, whose appearance confirmed 

 my reason for doubting the validity of variety 

 pyriforme. I may say that ast month (September, 

 1922), during a botanical visit to the West Coast of 

 Vancouver Island, I found the same rose with 

 pear shaped and globular fruits on the same plant. 

 I smiled, and said to my colleague, Prolessor 



Hutchinson, who was with me, "Variety pyri- 

 forme." Like Darwin I can prophesy that some 

 day a gall fly similar to one found at Kitsilano 

 will be discovered near the Great Central Lake on 

 Vancouver Island. 



Tables Are Turned — Plants Attack Animals 

 Animal Diseases Caused By Plants. 

 In the time at my disposal I cannot do more 

 than merely mention some instances of parasitism 

 where plants are the offenders and animals the 

 hosts; even man is not immune to attack by plant 

 parasites. Dandruff on the scalp is a fungus 

 similar to mildew, the so-called Ringworm is not 

 a worm but a fungus, like a mould, living on the 

 skin. Another mould is sometimes found in the 

 stomach of man, more frequently of horses, caus- 

 ing the disease known as Aspergillosis (named after 

 the fungus). The so-called vegetable-caterpillar 

 is merely a caterpillar skin filled up with woody 

 substance formed by a fungus which attacked the 

 living caterpillar, killed it, and used up all the 

 internal organs. Salmon disease which attacks 

 young fish and injured salmon is a skin disease 

 caused by another parasitic plant, and all our 

 bacterial diseases belong to the Schizomycetes or 

 splitting fungi — belonging to the vegetable king- 

 dom. Then we have the carnivorous plants which 

 capture and digest small animals. The ingenuity, 

 approaching sagacity, exhibited by the many 

 kinds of insect-eating plants, and by some which 

 entrap small crustaceans and other water animals, 

 is so extraordinary in its diabolical eflSicency that 

 to study them from an insect's point of view is to 

 invite hideous nightmares of tortures unsurpassed 

 by those which martyrs suffered in the dark ages. 

 Imagine walking along the street, when a door 

 suddenly opens and you are drawn by an unseen 

 hand into a dimly lighted room containing scores 

 of bodies in all stages of decomposition. From 

 the walls of the room shoots a fine spray of fluid 

 which dissolves your skin and flesh ; you are being 

 digested alive. This has been the experience of 

 millions of creatures which came into close prox- 

 imity to the bladder-like traps of the Bladderwort 

 which is to be found in Trout Lake, Vancouver, 

 and many other akes in British Columbi.i. 



The beautiful Sundew, which most of you have 

 seen on our Burnaby Lake Excursions, appears to 

 an insect as a deadly monster, like a giant devil- 

 fish with many fiery tentacles ready to seize and 

 devour the first creature to come into contact with 

 it. The baited traps of different Pitcher plants 

 which lure their prey by intoxicating drinks, then 

 drown the unfortunate victims in a digestive fluid; 

 and the miniature bear-traps of the Venus Fly- 

 trap and Aldrovandia, the latter an aquatic plant 

 like Bladderwort, all have their romantic story to 



