GRAY 



his personality and influence prevented any great defec- 

 tion. At the present time, the pendulum seems to have 

 swung to the opposite extreme. Species are small dis- 

 junctive groups: authors tend to make many rather 

 than few. It will probably be a decade or more before 

 the species-ideal swings back to the middle point, where 

 only a pendulum can rest. 



Gray was a philosophical naturalist. He was one of 

 the tirst of the great American naturalists to espouse 

 the main argument of D.arwin's "Origin of Species." 

 In this respect he stands in bold contrast to his great 

 colleague Agassiz. Gray's influence was the greater 

 because he was known to be a pronounced theist. He 

 entered the conflict which arose between organic evolu- 

 tion and theology, and did much to heal the schism. 

 His writings on the evolution controversies were pub- 

 lished in two volumes, "Darwiniana" and "Natural 

 Science and Religion." 



Gray was a constructive philosopher, as well as a 

 critic. His essay ou the "Relations of the Japanese 

 Flora to that of North America," was one of tlie first 

 masterful attempts to explain the principles of the dis- 

 tribution of species. This essay stands for the following 

 conceptions: that species have one origin; that distri- 

 bution over the earth is due to physical causes; that 

 the origin of the north temperate flora is circumpolar. 

 One who is unfamiliar with the points of view of his 

 time cannot catch the full significance of these conclu- 

 sions. They are now accepted, not challenged. Into 

 philosophical discussions of cultivated plants he made 

 few excursions, although his paper on the running 

 out of varieties has become a standard; and in his 

 manv reviews he made occasional contributions to this 

 field'. 



Asa Gray was a lovable man. He was gentle, quiet, 

 sweet-tempered; intellectually he was keen and pene- 

 trating. Both by his personality and his teaching, he 

 exerted an incalculable influence on American botany, 

 and, indeed, on American biological science. In Europe 

 he became a representative of what was best in Ameri- 

 can science. Harvard College, in which he held a pro- 

 fessorship from 1842 until his death , became the Mecca of 

 every American botanist. Here he built up the most 

 important herbarium and botanical library in the New 

 World. He was the master of American botany. 



Gray's writings were voluminous. He was known as 

 one of the most skilful of American reviewei's and bi- 

 ographers. His scattered untechnical writings were 

 repnbli.shed in two volumes in 1889, by Professor Sar- 

 gent, as the "Scientiflc Papers of Asa Gray." See the 

 "Letters of Asa Gray," 2 vols., 1893, by his widow. Jane 

 Loring Gray. L. H. B. 



GREENHOUSE. In America the word Greenhouse is 

 used generically for any glass building in which plants 

 are grown, with the exception of coldframes and hot- 

 beds. Originally and etymologically, however, it means a 

 house in which plants are kept alive or green: in the 

 Greenhouse plants are placed for winter protection, and 

 it is not expected that they shall grow. The evolution 

 of the true Greenhouse seems to have begun with the 

 idea of a human dwelling house. At first larger win- 

 dows were inserted; and later, a glass roof was added. 

 In early times it was thought best to have living rooms 

 above the Greenhouse, that it might not freeze through 

 the roof. Even as late as 1806, Bernard McMahon, 

 writing in Philadelphia, felt called upon to combat tliis 

 idea. The old or original conception of a Greenhouse as 

 a place for protecting and storing plants is practically 

 extinct, at least in America (Fig. 980). 



Other types of plant houses are the conservatory 

 (which see), in which plants are kept for display; the 

 forcing-house (see Forcing), in which plants are forced 

 to grow at other times than their normal season; the 

 stove or warmhouse ; the propagating pit. Originally 

 the warmest part of the plant-house, that part in which 

 tropical plants were grown, was heated by a stove made 

 of brick, and the house itself came to be called a stove. 

 This use of the word stove to designate the warmest 

 part or room of the range is universal in England, but 

 in America we prefer the word warmhouse (and this 

 word is used in this Cyclopedia). Originally, hothouse 

 was practically equivalent to stove, but this term is 



GREENHOUSE 



685 



little used in this country, and when used it is mostly 

 applied generically in the sense of Greenhouse. 



It will thus be seen that there is no one word which 

 is properly generic for all glass plant houses. The word 

 glasshouse has been suggested, and it is often used in 

 this work; but there are other glass houses than those 

 used for plants. It seems best, therefore, to use tlie 

 word Greenhouse for all glass buildings in which xdants 

 are grown; and usage favors this conclusion. 



The long, low Greenhouse range, of the type which 

 we now know in our commercial establishments, 

 probably had a different origin from the high-sided 

 Greenhouse. The glasshouse range appears to have de- 

 veloped from the practice of protecting fruits and other 



986. The old-time Greenhouse. 



With opaque roof and sash-made sides (Aber* 

 crombie, ITyti). 



plants against a wall. In European countries, particu- 

 larly in England, it is the practice to train fruits aud 

 other plants on stone or brick walls, in order that they 

 may be protected from inclement weather and receive 

 the greater sun heat which is stored up in the masonry. 

 It occurred to Nicholas Facio Duilhier to incline these 

 fruit walls to the horizon so that they would receive the 

 greater part of the incident rays of the sun at right 

 angles. He wrote a book on the subject of "Fruit-Walls 

 Improved," which was published in England in 1()99. 

 Facio was a mathematician, and he worked out the 

 principle of the inclined walls from mathematical con- 

 siderations. Such walls were actually built, but accord- 

 ing to the testimony of Stephen Switzer, who wrote in 

 1724, these walls were not more successful than those 

 which stood perpendicularly. Certain of these walls on 

 the grounds of Belvoir Castle, and over which grapes 

 were growing, received the additional protection of 

 glass sash set in front of the inclined walls and over 

 the vines. In addition to this, flues were constructed 

 behind the wall in order that heat might be given. The 

 construction of hollow heated walls was not uncommon 

 in that day. The satisfactory results which followed 

 this experiment induced Switzer to design glass-covered 

 walls. The "glasshouse" which he pictured in the 

 "Practical Fruit-Gardener "( 17H1 ) represents a Green- 

 house '^^i ft. wide in the clear. Fig. 987. At the back of 

 this house is an inclined heated wall on which the 

 grapes are grown. Three and one-half ft. in front of 

 this, a framework is erected to receive the sash. Tliere 

 are 3 tiers of openings or windows along the front, the 

 two lower ones of which are for window sash, and the 

 upper one is vacant in order to provide for ventilation 

 and to allow space to receive the lower sash when they 

 are lifted up. The whole structure is covered with a 

 roof or coping. Switzer declares that the introduction 

 of these covered, sloping walls "led the world " to the 

 "Improvement of glassing and forcing grapes, which 

 was never done to that Perfection in any Place as it is 

 upon some of the great Slopes of that elevated and 

 noble Situation of Belroir Cftstle/' Johnson, in his 

 "History of English Gardening," quotes the remarks of 

 Switzer, and makes the statement that the use of these 

 walls "led to the first erection of a regular forcing struc- 

 ture of which we have an account." The immediate out- 

 come of these covered walls seems to have been the 

 lean-to Greenhouse, and from that has developed the 

 double-span glass range of the present day. Long be- 

 fore Switzer's time plants were forced in a crude way, 

 even by the Romans, mostly by being placed in baskets 

 or other movable receptacles, so that they could be 

 placed under cover in inclement weather; but the im- 

 provements of Facio and Switzer seem to have been 



