NA TURE 



[November 7, 1907 



nised students " (formerly " King's scholars "), receiving 

 a grant from the Board of Education, who have matricu- 

 lated, and arc thus qualified to enter one of the schools 

 of the University for a three years' course, leading up to 

 the degree in arts or science. Concurrently with their 

 academic studies they take a course of professional in- 

 struction at the training college with a view to certifi- 

 cation by the Board. In addition to these students, there 

 is a smaller number of graduates who take a one year's 

 course in preparation for the University's diploma in 

 pedagogy, and intend to teach in secondary schools. Since, 

 however, a rapidly increasing proportion of the recognised 

 students enter with a higher qualification than matricula- 

 tion, and obtain the degree before the conclusion of the 

 three years' course, the work of the college will in a few 

 years become very largely post-graduate, and may be 

 expected to have an important influence upon the standard 

 of teaching in the elementary schools of London. 



Since every student is either a graduate or an internal 

 student of the University in arts or science, the equipment 

 of the college has been determined solely by the needs of 

 the professional side of the course of training. Thus the 

 laboratories, which together with the art studio occupy 

 the top floor of the building, are used almost entirely for 

 the demonstration of methods of teaching science subjects. 

 The larger laboratory (55 feet by 30 feet) contains benches 

 of a special design planned for elementary work in chem- 

 istry, physics, and mechanics, fume cupboards, a well- 

 equipped demonstration table, and teak tables used chiefly 

 in connection with the instruction in practical mathematics. 

 Between the mathematical and physical benches accom- 

 modation is provided for students following the course of 

 a lesson given to a class of children. 



The smaller laboratory (30 feet by 20 feet) is devoted to 

 nature-study. In addition to working benches, it is 

 equipped with specimen cases, a dark cupboard, and other 

 fittings. A balance room and a preparation room situated 

 between the two laboratories serve the needs of both. 

 There is also a small room (readily transformable into a 

 photographic dark room) equipped ' with water, gas, and 

 electric power, and intended to be used for anthropo- 

 metric work and for researches in pedagogical psychology. 



On the roof, within easy access from the laboratories, is 

 a plant house containing a large tank for aquatic plants 

 and animals. The level space around this is utilised as a 

 meteorological observatory in connection with lessons in 

 geography. Finally, on the floor below that already de- 

 scribed, is a pedagogical museum, which performs the 

 functions of a geographical laboratory. 



Carefully planned and closely correlated courses in 

 mathematics, geography, nature-study, and physical science 

 are taught in these laboratories to the children of the 

 demonstration schools by students under supervision. Most 

 of these students either have alre.adv graduated or are 

 . about to sit for the B.Sc. degree, and are paving soecial 

 attention during their last year to the teaching of the 

 scientific subjects of the curriculum. 



IMMUNITY TO DISEASE AMONG PLANTS.^ 

 'T'HE question of immunity to disease has been so closelv 

 studied and so frequently discussed in connection 

 with the diseases of man that it seemed to me that it 

 might be of interest to bring together some of the facts 

 now known to us about the incidence of disease among 

 plants and the theories which have been advanced as to 

 the cause of the immunity which some species and 

 varieties exhibit to various diseases. 



The late Prof. Marshall Ward has shown that Puccinia 

 dispcrsa, the brown rust of grasses, seems to exist in 

 several "biologic forms," each of w-hich attacks onlv 

 one group of nearly related species of Bromus, and the 

 same condition obtains in the Erisiphea?, or mildews, 

 according to Salmon. How is it that these fungi are 

 incapable of infecting such nearly related host plants as 

 are represented by the species within a single genus? 

 The suggestion was originally made that difTerences in 

 the thickness of the cell walls, fewer or smaller stomata, 



; df-Iivered at the annual mee'ine ol* the British 

 t Manchester by Prof. F. E. Weiss. 



NO. T984, VOL. 77] 



longer hairs, &c., were the obstacles which repelled the 

 fungi and rendered certain species and genera of plants 

 immune to the attacks of particular fungi. Working with 

 the different species of Brome, Marshall Ward was, how- 

 ever, able to show that there was no relationship between 

 the stomata, hairs, and so forth, and the infectibility 

 of the species. Immunity did not in any way depend 

 upon the anatomical characters of the host plant, but 

 entirely on physiological reactions of the protoplasm of 

 the fungus and of the cells of the host. In other words, 

 infection and resistance to infection depend on the power 

 of the fungus protoplasm to overcome the resistance of 

 the cells of the host by means of enzymes or toxins, and 

 reciprocally on the protoplasm of the cells of the host to 

 form anti-bodies which destroy such enzymes or toxins, 

 just as is the case with resistance of animal organisms 

 to their bacterial foes. Salmon has shown in his experi- 

 ments that susceptibility in a leaf normally immune to 

 the attacks of the biologic form of a particular mildew 

 may be induced by various mechanical means, such as 

 cutting the leaf or searing it with a red-hot point of a 

 knife, or by exposing the leaf to ether or alcohol vapours, 

 or by exposing it to heat. The resistant vitality is 

 thereby impaired, and the fungus gains the upper hand. 

 Plants, if not immune to a particular disease, may be 

 rendered so to a certain extent by similar methods to 

 those employed in the case of animals. More or less 

 successful injection experiments have been made in the 

 case of fruit trees suffering from chlorosis, and as a 

 result animal parasites have been got rid of as well. 

 Undoubtedly if the general vitality of the tree can be 

 raised some diseases can be thrown off. 



Marchal has stated, 1902, that young plants of the 

 lettuce could be rendered immune against Brcmia latucae 

 by feeding the plants with a solution of copper sulphate 

 (i in 30,000). This view has received support from 

 Laurent and Mass^e, but Salmon has not been able to 

 confirm these results. It will be seen that the views are 

 still somewhat conflicting, and too much must not be 

 e.xpected from such methods of treatment. 



The hope of the agriculturist lies in another direction. 

 Plants, like animals, are subject, as Darwin has shown, 

 to a considerable amount of variation, and all characters, 

 whether anatomical or physiological, are subject to change 

 or mutation. Immunity to disease, dependent as it is on 

 certain physiological peculiarities, the secretion of anti- 

 toxins, rather than on anatomical structure, is similarly 

 a subject of variation. We see this readily illustrated 

 when passing through a field exposed to some epidemic 

 disease, where here and there plants are found which 

 have been either only slightly damaged or not attacked 

 at all. These should be selected for breeding purposes, 

 and thus hardier varieties can be produced. Another 

 method which has shown itself useful for producing 

 resistant forms is by hybridising. It is a well-known 

 fact that hybrids, while partaking of the nature of one 

 or both of the parents in most characters, generally exceed 

 both in vegetative vigour — a characteristic to which the 

 sterility of some hybrids is attributed. But vegetative 

 vigour, as we have seen above, is generally associated 

 with immunity to disease, and hence hybrids are often 

 found to be more resistant. This is not always the case, 

 for in this respect hvbrids vary too, but the French 

 horticulturists MM. Bouttes and Guillon have been 

 successful in producing hybrid vines which are more 

 resistant to the mildew than either of the parents. 



In the selection of immune varieties one is faced with 

 the unfortunate fact that many of the most resistant 

 forms are the least valuable, producing poorer fruits and 

 seeds than the delicate forms. But by judicious hybrid- 

 ising this defect of the immune race can be largely 

 counteracted. Mr. Lewton Brain has collected a good 

 deal of information on this point. Both in the case of 

 vines and in wheat many disease-resisting forms have 

 been produced. 



In connection with cotton crops, it is remarkable how 

 great is the range of variation with regard to the resist- 

 ance of the olants to the wilt disease (Neocosmnsiiora 

 vasitifecta). By selection and suitable hybridising. Rivers 

 has been able to obtain varieties which remained un- 

 touched by the disease, while of the neighbouring crops 



