xxxvi. HYBRIDISING AND RAISING ORCHID SEEDLINGS. 



make considerable progress, and yet go off, if for any reason the ovules 

 should fail to be fertilised. 



Causes of Failure. — The period required for the development of the 

 pollen tubes and ovules varies considerably in different Orchids, and this 

 may represent one of the causes of failure when very distinct species are 

 intercrossed. When a species is fertilised with its own pollen all the forces 

 at work are in complete harmony, but when the pollen is derived from a 

 widely distinct species the rhythm may be completely upset. The pollen 

 may be capable of causing the development of the ovary and ovules, and yet 

 fail to effect fertilisation when the proper time comes. The pollen tubes 

 from a very distinct species may mature too soon or too late. Or they may 

 be too large to effect an entrance into the micropyle of the ovule of the other 

 species. Again, they may sometimes fail to reach the necessary length, or 

 there may be some other incompatibility or obstacle to their proper develop- 

 ment in the new combination. There are good reasons for the belief that 

 in most cases where the ovary develops as the result of pollination without 

 fertilisation being subsequently effected that the difficulty is largely a 

 mechanical one, and one of them is the fact that in many cases a few good 

 seeds are produced. There is also the well-known fact that in the case of 

 Cattleya crossed with Sophronitis, and of Brassavola crossed with Cattle3'a, 

 the fertile seeds are only found at the apex of the capsule. Again, Cattleya 

 can be crossed with Epidendrum, but the reverse cross fails, and the reason 

 is believed to be that the pollen tubes of Cattleya, and similar large-flowered 

 Orchids, are too large to enter the micropyle of the ovule. 



Maturing of the Capsule. — If the capsules survive the period just 

 mentioned — technically they cannot be called seed-capsules until after the 

 ovules are fertilised — they will probably mature and ripen. The period of 

 maturing varies greatly in different Orchids, and to some extent also under 

 varying conditions, but as this stage approaches it is advisable to watch for 

 the first sign of splitting, otherwise some of the seed may be lost. If the 

 capsule then appears mature it may be cut at once, or tied up securely in a 

 piece of loose tissue paper for a few days, so as to allow the seeds time to 

 mature fully. In practice it is a general custom to tie up the capsule when 

 nearly mature to prevent loss of the seeds before splitting is noticed, also to 

 prevent the seeds from falling and germinating where not wanted. 



Gathering the Seed. — When the capsule is cut it should be removed 

 to a dry shed, and as soon as ready may be opened, or the seed removed by- 

 tapping the capsule gently over a piece of tissue paper. As soon as any 

 seeds fall they should be examined with a good lens to see if they appear 

 perfect. If they appear plump in the centre and diminish considerably 

 towards the pointed ends, they may be considered good, but if they look like 

 hairs or chaff, without any thickening in the middle they are generally bad, 



