Reproduction. 69 



rain of 16.8 mm. during the preceding night, 4 ounces of seed (including 

 chaff) were sown at Station 7, in 5 rows, each a meter long. The ground 

 was previously cleared of all plants and thus loosened, and, the seed 

 having been left uncovered, the seedlings were exposed to full insolation. 

 On September 9 following, 119 seedlings were counted. 1 These compared 

 favorably in appearance and size with other seedlings found growing 

 spontaneously in the surrounding area. The seed was sown more thickly 

 than would occur in nature, and the number of seedlings was also much 

 greater, and far too great for their normal development. 2 



Comparison of these results with those obtained by observation of 

 germination in irrigated ground affords considerable interest. About 

 150 plants, placed in a small patch of ground by Mr. C. T. Andrews in 

 the spring of 1907, flowered freely during that and the following year. 

 A very large number of seeds must have been disseminated, notwith- 

 standing a good deal had been gathered, of which fully 30 per cent were 

 viable. During the summer of 1908, at the time (June) when seed was 

 germinating in the surrounding region under natural conditions, some 

 seedlings were observed. About 50 were counted, but in the whole 

 area (0.1 acre) there could hardly have been more than a few hundred 

 at the outside. Nor did they grow as well as field seedlings, perhaps 

 because of the rapid drying of the superficial layers of soil. The percent- 

 age of germination here must therefore have been exceedingly small, 

 and much less than that which occurred in experiment 192 above de- 

 scribed, and also than that which takes place in nature, if we may judge 

 by the numbers of seedlings actually found in the field in the summer 

 of 1908. The following observations are pertinent here: 



(1) Station 3. June 1908. In areas of 1 square meter, representative 



counts of 8 and 14. April 1909, 23 living seedlings of 1908 were 

 found on the whole quadrat (100 square meters). 



(2) The region about Stations 7 and 8. On June 24 a large number of 



seedlings was seen. 



(3) Station 2, quadrats 5 and 6. Sept. 12. Four seedlings 10 cm. apart. 



Nearby 6 seedlings 10 cm. apart. Several counts showed about 

 20 plantlets per square meter. None on previous visit to this 

 station, July 28. 



(4) In 1 square foot on the same area, 6 well-grown seedlings. Sept. 



12, 1908. 



(5) In a wire-fenced quadrat which was cleared of all plants (other 



than guayule) by Mr. C. T. Andrews early in 1907, 5 miles north 

 of Cedros in an open plain, leaving one tall guayule plant in the 

 middle, no seedlings appeared till after June. In September 29 

 seedlings were found within 6 feet of the plant, chiefly in one 

 direction. One mariola seedling was found. 



(6) Station 8, quadrat 1 (100 square meters). 24 seedlings, Sept. 1908. 



(7) In 4 square feet, on a loma north of Cedros, near Station 8, Aug.^ 8, 



31 seedlings, all of 1908 except one of 1907. This number in- 

 cluded one of Parthenium hysteropkorus. 



1 The largest of these had a stem (epicotyl) 1 cm. long, with leaves 4.7 cm. 

 long by 1.5 cm. broad. 



3 In April 1909 it was found that all the seedlings had been destroyed by goats. 



