8 



INTHonrcTION. 



rum (parent) 3/a and the average 1.5/*; and in B. cul- 

 verwellii (hybrid) 5ft and the average 3/t. In Menziesia 

 empetriformis var. the largest starch grains are 6/*, and 

 in all cast's they arc larger than in the other parent 

 Rhododendron chamcecistus; while in the hybrid Jlryan- 

 thus erectus the grains arc 1/j. across at their largest, 

 though most are from 2 to .fy, the size heing intermediate 

 but falling rather toward the latter parent. Macfarlane 

 states : 



" Hedychium gardnerianum, the one parent of 77. 

 sadleriiunuii . forms strong rhizomes, whose storing cells 

 are large, hut scantily filled with starch in all that I 

 have examined. Each starch grain is a small, flat, trian- 

 gular plate, measuring 10 to I'-V from hilum to base, 

 and the lamination is not very distinct. //. coronarium, 

 the other parent, forms smaller and fewer rhizomes, 

 and the starch-storing cells are from half to three-fourths 

 the size of the last, but these are densely filled, particu- 

 larly in the central parenchyma, with large starch gran- 

 ules. Each is ovate, or in some cases is tapered rather 

 finely to a point at the hilum. They are from 32 to 

 60/t long, measuring as before, and the lamination is 

 very marked. The cells of the hybrid are on the average 

 between these of the parents; but if one may judge by 

 opacity of cells the amount of stored starch approaches 

 more closely to that of the hitter parent. The grains 

 may best be described if we suppose a rather reduced one 

 of the first parent to be set on the reduced basal half of 

 one of the latter. The lamination also is more pro- 

 nounced than in the first, less so than in the second. 



" A second cross was effected by Mr. Lindsay with 

 II. coronarium, and examination of the rhizome starches 

 pro es that the second hybrid approaches very closely to 

 the species parent. But the grains of H. lindsayi illus- 

 trate microscopically a phenomenon which has been re- 

 idly referred to, viz, the greater variability and 

 instability of a second over a first hybrid; for many of 

 the grains (in some specimens the majority) have fantas- 

 hapes, appearing as if undergoing rapid disintegra- 

 tion by leucoplasts, or perhaps more truly as if the latter 

 were incapable of building up the shells of starch in a 



■dar and uniform manner. 



" A set of crosses has been effected between If. datum 

 and //. coronarium. The grains of the first are like those 

 of //. gwrdnerianum, except, that they are larger (18 to 

 and that the lamination is coarse. The grains of 

 the hybrid are larger than those of //. sadlerianum, and 

 exhibit even more evident lamellae. They measure on the 

 average, 40/t, but vary from 30 to 50/t. Not infrequently 

 all the above hybrids have (mixed up with grains more 

 illy intermediate) some grains which can scarcely, 

 if at all, be distinguished from the small ones peculiar 

 to one parent, while very rarely I have observed grains 

 so large and rounded as to pass for those of //. coro- 

 narium. Now, when de cribing the epidermal leuco- 

 - of Dianthus grii vei it was stated that, though the 

 average was nearly 3ft, some measured 2.5/i or slightly 

 others as much as 3.5ft. The occurrence of these, 

 and similar minute dn: in protoplasmic masses, 



or in formed materials like starch grains which are due 

 to manufacture by these masses, induced me to prepare 

 of micro photographs, and to project lantern trans- 



parencies of these on a ?-foot screen. Thus it wa.« pofi 

 sible to study their dimensions more exactly than under 

 the microscope. It was then found (hat while the shape, 

 appearance, and size of most stanh grains of Hedychium, 

 of Dianthus leucoplasts, and of Geum and Masdauallia 

 chromoplasts were intermediate, examples might he got 

 which reverted powerfully to one parent, and, so far as 

 they ha\e yet been studied, the revei'Mon was most fre- 

 quently towards the parent with the more minute cell- 

 contents." 



The results of the studies of starches are therefore 

 in entire accord with Macfarlane's conclusions pertaining 

 to tbe tissues in showing intermediateness of the hybrid, 

 with a tendency at times to a leaning to one parent. 



Investigations of the starches of varieties and of 

 parents and hybrids of varieties of round and wrinkled 

 peas have been made by Gregory (The New Phytologist, 

 1903, ii, 226), Weldon (Biometrica, 1902, i, 246), and 

 Darbishire (Proc. Roy. Soc, B., 1908, lxxx, 122 ; Breed- 

 ing and the Mendelian Discovery, 1912, 124); 



Gregory (Tbe New Phytologist, 1903, n, 226) found 

 that the starches of round and wrinkled peas occur in 

 two very different types. In the round seeds the periph- 

 eral cell-layers of the cotyledons contained a few oval 

 starch-grains which did not exceed 0.06 mm. in the great- 

 est diameter. In the third layer the grains reached 0.2 

 mm. in length, while the more deeply situated cells were 

 crowded with oval grains measuring as much as 0.34 mm. 

 in the greatest dimension. The grains were regular in 

 shape, with a definite center surrounded by well-marked 

 lines of stratification. In the wrinkled peas the grains 

 of the peripheral layers were of about the same size as 

 those of the round peas, but were of a different type, 

 occurring in irregular spheres with several centers, thus 

 forming a compound grain which has a strong tendency 

 to break up into smaller parts. In the cells which lie 

 deeply these compound grains never attain a greater 

 length than 0.1 mm. in the greatest dimension. Table 1 

 gives a list of the seeds examined. 



Table 1. 



Rare. 



Express 



Fillhasket 



Ties nain do Brotagne. . . 

 Maple (purple-flowered) 



Carter's Telegraph 



Victoria Marrow 



Field pea (purple flower) 



Purple Sugar 



William the First 



Telephone 



Laxton's Alpha 



Serpette nain blane 



Dark Jubilee 



Early Giant 



British Queen 



Windsor Castle 



Gregory notes that seeds of intermediate and dubious 

 hapes were not uncommon in certain of the races. The 



